Ecosystem alterations: Basic concepts for critical analysis

The following text is a summary of a lesson I conducted in a high school class, enriched with some documents gathered during its preparation. Given the interest sparked by this topic, which is certainly inadequate to fully address the complex issues it covers, I have added some updated bibliographic references to open new dialogues on the changes occurring in ecosystems, particularly those driven by human activities.

I chose to approach the subject without resorting to the strong and catastrophic tones often found in the media: those seeking confirmation of the end of the world and the rapid extinction of the human species may find this unsatisfactory. The approach aims to be balanced, systematically considering the sometimes contradictory findings emerging from the scientific community. It also highlights the issues of communication and perception, offering reflections on the relationship between scientific research and mass media.

Introduction

In recent years the delicate balance of ecosystems has undergone deep alterations due primarily to a drastic increase in human activities, on a global, regional and local geographical scale. The rapid development experienced during the post-war period in fact has led, in addition to countless benefits, also to many consequences for the environment, including the reduction of the ozone layer and the release of numerous pollutants.

The definition of ecosystem demands several important conceptual elements: energy, the biotic community, trophic chains, the exchange of matter and energy, the extension and balance of the ecosystem. These elements help to develop a model that allows us to understand the complex structure of an ecosystem and, in addition, to analyse its main alterations.

During this lesson we will try to answer the following questions: What is an ecosystem? What are its main elements? How have human activities altered ecosystems? How is this complex subject reported in the media and how is it perceived by the audience?

1. Ecosystem: suggestions for a definition

Exercise: Identify the main elements of an ecosystem. Why are we using the word system? Give me an example of a simple system and a complex system.

The term "ecosystem" first appeared in print in 1935, thanks to Arthur George Tansley and his work The Use and Abuse of Vegetational Terms and Concepts. In this volume, Tansley introduced some foundational ideas: organisms are part of a system characterized by interactions between biotic elements and environmental resources. He defined it as: "the fundamental concept appropriate to the biome considered together with all the effective inorganic factors of its environment is the ecosystem." These ecosystems serve as fundamental units of the natural environment and vary widely in size and type.

In 1953, American biologist Eugene Pleasants Odum published a landmark volume in academic studies of the field, titled Fundamentals of Ecology. In it, Odum revisited and expanded the concept of the ecosystem, defining it as "a unit that includes all the organisms of a given area interacting with the physical environment in such a way that the flow of energy leads to a well-defined trophic structure, biotic diversity, and material cycling within the system."

Over the following decades, other definitions emerged, refining these foundational concepts. Some focus solely on biotic components, equating the ecosystem to a series of trophic networks. Others broaden the scope to include abiotic components, such as the physical conditions of the environment.

To better capture the complexity of an ecosystem, it is worth adopting a definition that considers both biotic and abiotic components together. This perspective sees the ecosystem as a system spanning a specific area, characterized by relationships between living communities (biotic elements) and the physical environment (abiotic elements), developing in a dynamic equilibrium that evolves over time. In essence, an ecosystem is a nonlinear complex system that includes, importantly, humans and anthropogenic elements, as well as interconnections to and from other systems.

2. Structure

Solar energy is at the basis of the biotic component. This, as a whole, works like an organism in which all life forms are linked together. If one element were missing, the physiognomy of the community would adapt accordingly, taking on a new organization (biocenosis).

The biotic community creates a set of trophic networks that are interconnected. We can break down this network into three main categories of elements:

• Producers, such as vegetables that process organic substances from minerals. 
• Consumers, which directly or indirectly feed on organic substances provided by producers. 
• Decomposers, which decompose dead organisms and organic substances, returning them to the mineral state. 

In an ecosystem we have different flows of matter and energy. The vegetable kingdom gathers solar energy; a part of this is not used, the other part supports the synthesis of organic matter. Only a portion of this mass is assimilated by herbivores. The other portion is transformed by decomposers. A part of the matter integrated by herbivores (the rest is lost with excrement or through breathing) can subsequently be used by carnivores. As we can see, energy transfers take place at every stage; and at each stage there are also substantial energy losses.

This circular relationship simplifies the organization of trophic networks. Biocenosis can be analysed by considering plant and animal elements that make up the trophic network, their relationships and the ability to use physical components of the ecosystem. It is characterised by two principles:

1. Numerous and rich abiotic components correspond to numerous biotic communities.
2. If living conditions become more difficult, the number of species decreases, but each species records a population increase.

3. Properties

The ecosystem has the following properties (Vallega, 1995, p. 66):
- It is a real system: its elements have closer relationships than those related to the external environment (interconnective capacity).
- It is composed of organic elements (trophic networks) and inorganic elements:

• Hydrosphere : Water-climate system.
• Lithosphere : Earth-atmosphere interface.
• Atmosphere : Energy-atmosphere system.

- It has its own organization (biocenosis).
- It is a dynamic ever-evolving system.
- It is able to continue to complete its functions even in the presence of external impulses (resilience).

 

Each ecosystem has one or more habitats on which the survival of a species depends. The biotic community is made up of a variable number of species, animals and plants. We can distinguish two main groups: The first is characterized by few species, each of which has a large number of individuals, to the point of becoming dominant species. The second is characterized by a high number of species, each of which has a reduced number of individuals. These are rare species.

Example of species diversity. Diagram shows marine ecosystems: the y-axis shows the number of species, while the x-axis represents the population for each category of species. Tropical Low Waters (ABT), Deep Waters (AP), waters above the Continental Platform (PC), Low Boreal Waters (ABB), Boreal Estuaries (EB).

Factors influencing the dynamics of the ecosystem are numerous, such as the presence or absence of water resources, food, wind, location, temperature, exposure, pedology, or man.

4. Geographical scale

Ecosystems can be defined at various geographical scales. For example, a rainforest is a global ecosystem stretched over the equator. In its turn, it is composed by smaller ecosystems where biotic and abiotic aspects take on different characteristics. We refer to the ecosystem in both cases: the entire extension of the rainforest and the parts in which it breaks down.

Gerarchia spaziale dei sistemi ecologici (Massa, 1999)

Classification of large ecosystems based on the identification of biomes (Vallega, 1995):

• Rainforest (Southeast Asia, Africa, Northeast Australia)
• Rainforest with dry season, monsoon forest (Southeast Asia)
• Temperate forest in regions with heavy rains (Eastern Australia)
• Rainforest mountain forest
• Deciduous temperate forest (Eastern United States, Western Europe)
• Evergreen temperate forest
• Taiga (North America, Eurasia)
• Dwarf forests
• Acacia forests
• Shrub formations in arid climate
• Temperate forest
• Shrub coverings
• Savannah (Africa, South America)
• Prairie and steppe (Eurasia, New Zealand)
• Alpine forest
• Arctic tundra (Asia, North America)
• Tropical desert (North Africa, Asia Minor, western South America)
• Warm temperate desert (South and Central Asia, Australia, Argentina)
• Desert with scrub (western United States, inner Asia)
• Mountain desert
• Marshes
• Forest in continental wetlands (Amazon basin)
• Forest in areas of contact between fresh and salt waters (south-eastern United States)
• Mangrove forest (intertropical coasts and estuaries)
• Coastal wetland
• Pelagic marine environment
• Benthic marine environment
• Rocky coast
• Sandy coast
• Estuary
• Lake
• River

Creating classifications and types of large ecosystems does not present big difficulties. The operation may be harder at local level.

5. How to define an ecosystem?

Geography is a discipline that is often concerned with defining a phenomenon on the territory. The problem to limit an ecosystem is particularly complex. If we assume a basic definition of ecosystem, such as a series of food chains, the boundaries are relatively simple to define. The difficulties increase if we include other components and relationships that characterize them.

Exercise : Put down on a piece of paper the limits of a natural park or reserve in your region: 1 - define main elements of the ecosystem. 2 - what kind of relationships can you see between those elements? 3 - how to delimitate the ecosystem? 4 - what are anthropic elements that characterize the park or its borders? 

6. Alterations of the ecosystem: an evolutionary system

When ecosystems register external inputs, they adjust in different ways. Most oh them would modify part of their organization, using their autopoietic abilities (ability to react to inputs).

However, external forces can be so intense that they challenge the entire ecosystem organization, transforming or destroying parts of the trophic networks. The result is a new ecosystem that takes place of the modified one. In this case autopoietic abilities are not enough and morphogenesis, structural change, arises.

The climax is the final equilibrium situation achieved after a long process of ecological succession.

We can identify two main categories of external impulses: alterations caused by human activities and alterations inside or outside components of the system.

6.1. Ecosystem alterations: internal and external alterations to the system

Too often, nature is perceived as synonymous with balance and inherently positive. In reality, numerous natural factors, both internal and external to the system, intervene to alter the state of ecosystems. These factors can include climatic changes such as altered energy input, the presence or absence of water, temperature fluctuations, or variations in light and wind. These elements significantly impact the structure of ecosystems.

Generally, these changes are slow and gradual, particularly regarding topography and soil formation. However, sudden and dramatic natural events such as floods, landslides, volcanic eruptions, droughts, and hurricanes can cause instant disruptions.

Below are some examples of disturbance processes, along with a brief outline of their potential effects on biotopes and species (Massa, 1999):

• Cause: Earthquake
  Effect: Landslides, erosion, substrate change
  Environmental changes: Substrate changes, damage/destruction of vegetation
  Affected biotopes: All biotopes in high-energy relief areas
  Generated habitats: Open terrains, steep slopes
  Favored biocenoses: Pioneer species, open-ground species

• Cause: Avalanches
  Effect: Landslides, erosion, substrate change
  Environmental changes: Substrate changes, damage/destruction of vegetation
  Affected biotopes: All biotopes in high-energy relief areas
  Generated habitats: Open terrains
  Favored biocenoses: Pioneer species, open-ground species

• Cause: Sea level changes
  Effect: Flooding, drainage
  Environmental changes: Moisture variation, wave impact
  Affected biotopes: Coastal areas
  Generated habitats: Salt meadows
  Favored biocenoses: Salt-meadow biocenoses

• Cause: Heavy rain/depressions
  Effect: Flooding
  Environmental changes: Moisture variation, wave impact
  Affected biotopes: Streams and rivers
  Generated habitats: Open sand and gravel banks
  Favored biocenoses: Pioneer species, open-ground species

• Cause: Lightning strikes/spontaneous combustion
  Effect: Fire
  Environmental changes: Mineralization, increased light on the ground
  Affected biotopes: Dry shrubs and forests
  Generated habitats: Initially open areas without vegetation, later flourishing flowering plants
  Favored biocenoses: Light-requiring species, nutrient-rich habitat species, pioneer species

• Cause: Wind/storms
  Effect: Tree falls
  Environmental changes: Damage/destruction of vegetation, increased ground light
  Affected biotopes: Dry shrubs and forests
  Generated habitats: Open spaces with flowering plants, standing (dry) and fallen (moist) deadwood
  Favored biocenoses: Deadwood species, decomposers, pioneer species, light-requiring species

• Cause: Heavy snowfall/frost
  Effect: Tree falls (snow/ice weight)
  Environmental changes: Damage/destruction of vegetation
  Affected biotopes: Dry shrubs and forests
  Generated habitats: Standing (dry) and fallen (moist) deadwood
  Favored biocenoses: Deadwood species, decomposers

• Cause: Severe frost combined with water-level changes
  Effect: Ice formation/movement
  Environmental changes: Damage/destruction of vegetation, ground cracks
  Affected biotopes: Shores (lakes, seas)
  Generated habitats: Open terrains, steep slopes
  Favored biocenoses: Open-ground species

• Cause: Mega-herbivores, ground burrowers
  Effect: Tracks, burrows, soil openings
  Environmental changes: Damage/destruction of vegetation, material deposition
  Affected biotopes: Shrubs, forests, grasslands
  Generated habitats: Open terrains, standing (dry) and fallen (moist) deadwood
  Favored biocenoses: Pioneer species, open-ground species, light-requiring species

• Cause: Beaver activity
  Effect: Dam building, water-level changes
  Environmental changes: Flooding of nearby shore areas, stagnant water and sediment zones, forest vegetation openings
  Affected biotopes: Running water and flood zones
  Generated habitats: Pools, shallow waters, wet meadows, marshes, deadwood
  Favored biocenoses: Wet-meadow, marsh, stagnant-water species, deadwood species

• Cause: Insect infestations
  Effect: Damage caused by insects
  Environmental changes: Damage/destruction of vegetation
  Affected biotopes: Shrubs and forests
  Generated habitats: Standing (dry) deadwood
  Favored biocenoses: Deadwood species, light-requiring species

Exercise 3
List examples of disturbance elements from recent news reports, specifying their impact on ecosystems.

6.2. Ecosystem alterations: human activity

Human activity is a significant source of ecosystem alterations on various scales, from global to local. Human presence has not only impoverished and degraded ecosystems but has also facilitated the emergence of new ones, such as agricultural, viticultural, and urban ecosystems. One often overlooked alteration involves genetic manipulation: biotechnology is a rapidly growing field with increasing impacts on agricultural and other ecosystems. However, this aspect will not be explored in detail in the following text, to focus instead on a traditional perspective.

Exercise
Based on your knowledge, create a list on the board of human activities that, according to your current understanding, have the greatest impact on ecosystems. Rank them from the most significant to the least significant. At the end, compare the result with the data presented in the table below, which outlines total greenhouse gas emissions by sector.

Settore	Percentuale delle emissioni complessive
Energia (elettricità,riscaldamento, trasporto)	73.2
- Trasporto su strada (auto, bus, camion,ecc.)	11.9
- Trasporto aereo (commericiale e passeggeri)	1.9
- Trasporto ferroviario (commericiale e passeggeri)	0.4
- Trasporto pipelines (oleodotti, gas, acqua, ecc.)	0.3
- Trasporto marittimo (commericiale e passeggeri)	1.7
- Edifici residenziali (luce, cucina, riscaldamento, ecc.)	10.9
- Edifici commerciali come ristoranti, uffici e negozi	6.6
- Produzione di ferro e acciaio	7.2
- Produzione di metalli non ferrosi (rame, zinco, titanio, ecc.)	0.7
- Produzione meccanica	0.5
- Trasformazione prodotti per cibo e tabacco	1
- Produzione cartacea e tipografica	0.6
- Produzione chimica e petrolchimica come fertilizzanti, farmaceutica, ecc.	3.6
- Altre industrie (tessile, mineraria, ecc.)	10.6
- Energia utilizzata in agricultura e nella pesca	1.7
- Altre emissioni legate alla produzione di energia (nucleare, biomassa, idroelettrica, ecc.)	7.8
- Emissione legate all’estrazione del carbone	1.9
- Emissioni legate all’estrazione di petrolio e gas	3.9
Agricultura, foreste e utilizzo del suolo	18.4
- Allevamento e letame	5.8
- Risaie	1.3
- Suoli destinati all’agricultura (fertilizzanti)	4.1
- Incendio degli scarti di produzione (riso, canna da zucchero, ecc.)	3.5
- Foreste	2.2
- Gestione dei terreni coltivati	1.4
- Gestione dei prati	0.1
Processi industriali	5.2
- Cemento, emissione del processo produttivo (emissioni supplementari presenti sotto Energia)	3
- Chimica e petrolchimica (emissioni supplementari presenti sotto Energia)	2.2
Rifiuti	3.2
- Discariche (produzione di metano dalla decomposizione di materia organica)	1.9
- Acque reflue (produzione di metano da scarti organici)	1.3

Emissioni complessive di gas a effetto serra, per settori (fonte: OurWorldinData.org, Hannah Ritchie, 2020)

Emissions come from many sectors: we need many solutions to decarbonize the economy
It is clear from this breakdown that a range of sectors and processes contribute to global emissions. This means there is no single or simple solution to tackle climate change. Focusing on electricity, or transport, or food, or deforestation alone is insufficient.
https://ourworldindata.org/emissions-by-sector#energy-electricity-heat-and-transport-73-2 

6.2.1. Alterations on a global scale

Overall, human society plays an increasing role not only in ecosystems dynamics on a local scale, but also in biogeochemical cycles on a planetary scale. On global level we can define three main types of alteration (Primack R.B., Carotenuto L., 2003):

1. Land surface: Land use and resource extraction have transformed a growing part of land surface. Interventions can be of different nature: destruction, fragmentation, pollution, exploitation, manipulation, transformation.
2. Nitrogen cycle: Every year activities such as cultivation of nitrogen-fixing plants, use of nitrogen fertilizers or fossil fuels release more nitrogen composites in terrestrial systems than those released by natural processes.
3. Atmospheric carbon cycle: According to some authors, within the middle of the XXI century the use of fossil fuels will double the amount of carbon dioxide present in atmosphere.

These interventions have caused significant alterations to the habitats of numerous species, creating potential challenges for their survival. In recent decades, there has been an increase in the number of threatened species, a trend that should be considered in relation to the growing reference population.

Gruppo	Numero approssimativo di specie	Numero di specie minacciate	Percentuale di specie minacciate
Vertebrati
Pesci	24’000	42	2
Anfibi	3’000	59	2
Rettili	6’000	167	3
-Boidae (boa)	17	9	53
-Varanidae (varani)	29	11	38
-Iguanidae (iguana)	25	17	68
Uccelli	9’500	1’029	11
-Anseriformes (anatre, oche, cigni)	109	36	33
-Psittaciformes (pappagalli)	302	118	39
Mammiferi	4’500	505	11
-Marsupialia (marsupiali)	179	86	48
-Canidae (lupi e cani selvatici)	14	11	79
Piante
Gimnosperme	758	242	32
Angiosperme	240’000	21’895	9
-Palmae	2’820	925	33

Numero di specie minacciate di estinzione per i maggiori gruppi di piante e animali, con indicazioni anche su alcune famiglie e ordini per i quali sono disponibili i dati (Primack, 2003)

6.2.2. Population growth

Human population growth and consequent increase in natural resources consumption is one of the major causes to ecosystem alteration. Until a few centuries ago, population evolution has been measured and marked by Malthusian cycle. Industrial Revolution is a point of rupture and has determined an acceleration in its growth.

Population went from one billion people in 1850 to two billion in 1930 and 6 billion in 1998. Reasons for this growth are the decrease in mortality and a birth rate that remained almost constant during the XX. century. In the early 2000s a slowdown in growth has been recorder for the first time: according to UN experts we are moving towards a new phase of balance that will bring the world population to stabilize at around 11 billion by 2100 (https://www.un.org/en/global-issues/population).

Demographic increase has important consequences on natural resources consumption and on alterations of the ecosystems. Large industrial and commercial activities are responsible for impacts that affect local and global environments. Mines, industrial fishing, deforestation, intensive agriculture, wetland recuperation, construction of dams, are just a few examples of human activities related to this trend.

Gruppi di specie minacciate	Degradazione e distruzione dell’habitat	Inquinamento	Sovra-sfruttamento	Competizione o predazione da parte di specie esotiche	Malattie
Tutte le specie (1'880)	85	24	17	49	3
Tutti i vertebrati (494)	92	46	27	47	8
-Mammiferi (85)	89	19	47	27	8
-Uccelli (98)	90	22	33	69	37
-Anfibi (60)	87	47	17	27	0
-Pesci (213)	97	90	15	17	0
Tutti gli invertebrati (331)	87	45	23	27	0
-Mitili d’acqua dolce (102)	97	90	15	17	0
-Farfalle (33)	97	24	30	36	0
Piante (1'055)	81	7	10	57	1

Percentuale di specie influenzate negativamente da ciascun fattore negli Stati Uniti; Le specie possono essere influenzate da più di un fattore e perciò il totale delle percentuali per ciascuna riga non è pari a 100. Per esempio l’87% delle specie di anfibi risente negativamente della degradazione e della distruzione dell’habitat e il 47% delle stesse specie è influenzao anche dall’inquinamento (Primack, 2003)

 
The assessments of researchers do not align with the dire predictions made in early demographic studies from the 1960s and 1970s, such as Paul R. Ehrlich's famed publication The Population Bomb (1968). New technologies, combined with more efficient resource use and recycling, have significantly mitigated the severity of impacts on ecosystems. Additionally, the general improvement in living conditions in countries with high population growth rates contributes to a reduced impact on natural resources, particularly biomass.

6.2.3. Degradation

Even when an ecosystem is not directly affected by destruction or fragmentation, human activities can play an important role in its specific structure. The cenoses are often damaged by external factors, which in the early stages of alteration process do not affect dominant species and therefore the impact is not immediately evident. Over time, the composition and structure of the system tends to adapt to new conditions determined by the degradation of the ecosystem.

The most frequent form of degradation is pollution, mainly caused by pesticides, synthetic fertilizers, chemicals, sewage, industrial sewage, urban settlements, intensive agriculture, toxic gases. Their presence is not always perceptible. Pollution can affect the climate, the quality of water, air and soil, posing a threat to biodiversity and finally it is a potential danger to human health. 

6.2.4. Local scale alterations

At the local level alterations affect well-defined ecosystems: a forest, a swamp, a meadow. Actions that could compromise the stability of an ecosystem are different: deforestation, land reclamation, agriculture, tourism infrastructure or settlements development. In this case, the importance of anthropic impacts has led to the birth of a particular ecosystem: urban ecosystem . The biotope is composed of natural and artificial physical elements such as constructions, communication networks, sewer systems, ... The urban biocoenosis is the association of all organisms living in urban biotope: plant population (phytocoenoses), animal (zoocenosis) and human (anthropocenosis).

The main characteristic of this system is the strong demand for resources and energy from outside. This generates several problems:

• Strong ecological footprint of urban system: strong incidence of this spatial set on other local, regional and continental ecosystems. Internal processes of the city require a lot of energy and matter.
• Poor autonomy: anthropocenosis fails to continue without continuous external contributions to urban system.
• Imperfect metabolism: the system produces a large amount of waste and emissions.

In conclusion, we can highlight how global and local alterations are interconnected, leading to both immediate and gradual changes in different ecosystems. Ecosystems tend to seek new equilibriums, and the assessment of impacts should not necessarily be negative. For example, deforestation results in a significant alteration of the original ecosystem, but the presence of open fields or varied landscapes can create ideal conditions for biodiversity. Evaluation metrics should therefore be adapted to avoid biases that could influence their outcomes.

Exercise: take a postcard of your city dating from the beginning of twentieth century: what considerations can you depict from it compared to the present? Take a piece of paper and try to schematize urban development on a spatial level. In another scheme, try to imagine how your city will be set up in 50 years from now.

7. Conclusions

To sum up, ecosystems are composed of two fundamental elements: biocenosis and one or more biotopes. Relationships are constituted by trophic chains and ecological cycles (circulation of matter and energy). It is an open system: system’s input is solar energy, its output are biomass and thermal energy.

As we have seen, ecosystem and its alterations can involve a great number of difficulties. Applying the concept of ecosystems it is important to focus on some fundamental aspects: the definition of the main constituent elements and the analysis of their behaviour in relation to the solicitations they receive. In fact, it is impossible to know everything about the trophic chains, the abiotic aspects or the relationships between different elements.

Men (individual, group, society) have developed functions that require a significant use of resources: to live, work, study, have fun or communicate. Ecosystems, territories, spaces take in different roles that evolve over time.

“I would like there to exist places that are stable, unmoving, intangible, untouched and almost untouchable, unchanging, deep rooted; places that might be points of reference, of departure, of origin: My birthplace, the cradle of my family, the house where I may have been born, the tree I may have seen grow (that my father may have planted the day I was born), the attic of my childhood filled with intact memories . ..

Such places don't exist, and it's because they don't exist that space becomes a question, ceases to be self-evident, ceases to be incorporated, ceases to be appropriated. Space is a doubt: I have constantly to mark it, to designate it. It's never mine, never given to me, I have to conquer it.

My spaces are fragile: time is going to wear them away, to destroy them. Nothing will any longer resemble what was, my memories will betray me, oblivion will infiltrate my memory, I shall look at a few old yellowing photographs with broken edges without recognizing them.”

(Perec, Georges, and John Sturrock. 2008. Species of spaces and other pieces. London: Penguin Books)

In conclusion, it is essential to always consider that the human species is, in fact, a component of natural systems. The dichotomy between humanity and nature is one possible narrative but not necessarily the most relevant. Being part of the system, humans interact, create, destroy, and transform energy, resources, and matter in ways no other species can. It is difficult to determine to what extent humanity acts as an agent or simultaneously as a victim within the complex, self-organizing, and sometimes convoluted balances in which it exists.

Looking at the many predictions made about the future, it becomes clear that we are not particularly skilled in this type of exercise. Future analysis often remains a chimera, shaped by our desires, fears, perceptions, prejudices, and imagination. The outcomes of these analyses reveal far more about the present than they do about the future.

In recent decades, many small steps forward have been taken in environmental policy and the social development of human communities. It is important to recognize and appreciate the progress made while continuing to address the numerous challenges that still affect the different dimensions of sustainability.

8. Readings

A problem of definition: nature and Anthropocene
Right now, humans can make their crops and their timber, to pasture their animals. If you added up to the human beings, we would weigh 10 times as much as the wild mammals put together. We cut roads through the forest. We have added little plastic particles to the sand on ocean beaches. We have changed the chemistry of the soil with our artificial fertilizers. And of course, we've changed the chemistry of the air. I know when you take your next breath, you will be breathing in 42 percent more carbon dioxide than you were breathing in 1750. I know all of these changes, and many others, how to kind of lumped together under this rubric of the "Anthropocene." This is a term that some geologists are suggesting we should give to our current epoch, given how pervasive human influence has been over it. Now, it's still just a proposed epoch, but I think it's helpful to think about the magnitude of human influence on the planet.

So where does this put nature? What counts as nature in the world where everything is influenced by humans?

I know 25 years ago, environmental writer Bill McKibben said that because of the climate change. In fact, he called his book "The End of Nature."

I disagree with this. I just disagree with this. I disagree with this definition of nature, because, fundamentally, we are animals. Right? Like, we evolved this planet in the context of all the other animals with which we share a planet, and all the other plants, and all the other microbes. And so I think that nature is not that which is untouched by humanity, man or woman. I think that nature is everywhere where there are multiple species together, anywhere that's green and blue and filled with life and growing. And under that definition, things look a little bit different.

Now, I understand that there are certain parts of this nature that speak to us in a special way. Places like Yellowstone, or the Mongolian steppes, or the Great Barrier Reef or the Serengeti. Places that we think of kind of representations of nature before we screwed everything up. They are less impacted by our day to day activities. Many of these places have no roads or few roads, so on, like such. But ultimately, even these Edens are deeply influenced by humans.

Now, let's just take North America, for example, since that's where we're meeting. So between about 15,000 years ago, when people first came here, they started a process of interacting with nature that led to extinction of large, large animals, from the mastodon to the giant ground, saber-toothed cats, all of these cool animals that unfortunately are no longer with us. And when those animals went extinct, you know, the ecosystems didn't stand still. Massive ripple effects changed grasslands into forests, So even in these Edens, in these perfect-looking places that seem to remind us of humans, we're essentially looking at a humanized landscape. Not just these prehistoric humans, but historical humans, indigenous people all the way up until the moment when the first colonizers showed up. And the case is the same for the other continents as well. Humans have just been involved in nature in a very influential way for a very long time.

Now, just recently, someone told me, "Oh, but there are still wild places."
And I said, "Where? Where? I want to go."
And he said, "The Amazon."

And I was like, "Oh, the Amazon. I was just there. It's awesome. National Geographic sent me to Manú National Park, which is in the Peruvian Amazon, but it's a big chunk of rainforest, uncleared, no roads, protected as a national park, one of the most, in fact, biodiverse parks in the world. And when I got there with my canoe, what I did, but people. People have been living there for hundreds and thousands of years. They just do not float over the jungle, they grow crops, they grow domestic crops, they are their houses. make pets out of animals That we consider to be wild animals. These people are there and they're interacting with the environment in a way that's really meaningful and That you can see in the environment.

Now, I was with an anthropologist on this trip , and he told me, as we were floating down the river, he said, "There are no demographic voids in the Amazon." This statement has really stuck with me, because it is that the whole Amazon is like this. There's people everywhere. And many other tropical forests are the same, and not just tropical forests. People have influenced ecosystems in the past, and they continue to influence them in the present, even in places where they're harder to notice.

So, if all of the definitions of nature that we might want to use that involve it being untouched by humanity or not having people in it, if all of those actually give us a result where we don't have any nature, then maybe they're the wrong definitions. Maybe we should define it by the presence of multiple species, by the presence of a thriving life.

Source: Emma Marris: Nature is everywhere - we just need to learn to see it , TED Talk. https://www.ted.com/talks/emma_marris_nature_is_everywhere_we_just_need_to_learn_to_see_it/transcript?language=en 

 

Balance and perception

Have you heard people say that humans used to live in balance with nature?
Well, yes, there was a balance. But let’s avoid the rose-tinted glasses. Until 1800, women gave birth to six children on average. So the population should have increased with each generation. Instead, it stayed more or less stable. Remember the child skeletons in the graveyards of the past? On average four out of six children died before becoming parents themselves, leaving just two surviving children to parent the next generation. There was a balance. It wasn’t because humans lived in balance with nature. Humans died in balance with nature. It was utterly brutal and tragic.
Today, humanity is once again reaching a balance. The number of parents is no longer increasing. But this balance is dramatically different from the old balance. The new balance is nice: the typical parents have two children, and neither of them dies. For the first time in human history, we live in balance.
Source: Rosling, 2018

In Rosling's text, a recurring theme is introduced: perception and the role of mass media. To stay on the theme of alterations of ecosystems, one of the most common chapters in world media is global warming. If on the one hand the media report a scientific fact, on the other they do it with a particular emphasis.

Exercise :

Look at the first graph (source: NASA) and comment on it in class. If you were a journalist, what title would you give to the article accompanying this image? Have you ever found similar titles or graphics in the media?

Now look at the second graph (source: Glen Fergus, 2014) and repeat the activities proposed for the first graph. Remember that the two graphs are both correct, only the scale changes. 

 

human apocalypse

In the mid-1970s it was briefly fashionable for journalists to write scare stories about the recent cooling of the globe, which was presented as undiluted bad news. Now it is fashionable for them to write scare stories about the recent warming of the globe, which is presented as undiluted bad news. Here are two quotes from the same magazine three decades apart. Can you tell which is about cooling and which about warming? The weather is always capricious, but last year gave new meaning to the term. Floods, hurricanes, droughts – the only plague missing was frogs. The pattern of extremes fit scientists’ forecasts of what a ——world would be like. Meteorologists disagree about the cause and extent of the ——trend, as well as over its specific impact on local weather conditions. But they are almost unanimous in the view that the trend will reduce agricultural productivity for the rest of the century ... The longer the planners delay, the more difficult will they find it to cope with climatic change once the results become grim reality. The point I am making is not that one prediction proved wrong, but that the glass was half empty in both cases. Cooling and warming were both predicted to be disastrous, which implies that only the existing temperature is perfect. Yet climate has always varied; it is a special sort of narcissism to believe that only the recent climate is perfect. (The answer by the way is that the first one was a recent warning about warming; the second an old warning about cooling – both are from Newsweek .)

(...)

Globally, tropical cyclone intensity hit a thirty-year low in 2008. The cost of the damage done by hurricanes has increased greatly, but that is because of the building and insuring of expensive coastal properties, not because of storm intensity or frequency. The global annual death rate from weather-related natural disasters has declined by a remarkable 99 per cent since the 1920s – from 242 per million in the 1920s to three per million in the 2000s.

(...)

The four horsemen of the human apocalypse, which cause the most premature and avoidable death in poor countries, are and will be for many years the same: hunger, dirty water, indoor smoke and malaria, which kill respectively about seven, three, three and two people per minute. If you want to do your fellow human beings good, spend your effort on combating those so that people can prosper, ready to meet climate challenges as they arrive.

Maps that show us who we are (not just where we are)

There are a huge number of good news stories in the world. Infant mortality is falling and has been falling at an incredible rate. A few years ago, the number of babies dying in their first year of life in the world fell by five percent in just one year. More children are going to school and learning to read and write and getting connected to the Internet and going on to go to university than ever before at an incredible rate, and the highest number of young people going to university in the world are women, not men. I can give you good news story after good news story about what is getting better in the planet, but we tend to concentrate on the bad news that is immediate. Rebecca Solnit, I think, put it brilliantly, when she explained: "The accretion of incremental, imperceptible changes which can constitute progress and which render our era dramatically different from the past" — the past was much more stable — "a contrast obscured by the undramatic nature of gradual transformation, punctuated by occasional tumult." Occasionally, terrible things happen. You are shown those terrible things on the news every night of the week. You are not told about the population slowing down. You are not told about the world becoming more connected. You are not told about the incredible improvements in understanding. You are not told about how we are learning to begin to waste less and consume less.
Source: Dorling, Danny. Maps that show us who we are (not just where we are). https://www.ted.com/talks/danny_dorling_maps_that_show_us_who_we_are_not_just_where_we_are 

 

9. Ecosystem Alterations: Frequently Asked Questions

Is it true that we have only a few years left before the end? Are we at risk of extinction?

Humans have always prophesied their own end, it is likely a cultural fact independent of objective metrics. Historically, where man ventured out of his comfort zones, he tended to expect the worst, imagining his end or that of the whole world. Not surprisingly, old geographic maps often represent, along the borders, a fairly clear indication: hic sunt leones or also hic sunt dracones.

To say that we are on the brink of extinction is a reckless and unfounded statement, especially in light of the macro-trends (population growth and life expectancy for example). As some researchers claim, the opposite may also be true, that is, man is able to harness his adaptive capacities and technologies to avoid an event that would normally have led to the extinction of the species (see for example Juan Enriquez, https://www.ted.com/talks/juan_enriquez_we_can_reprogram_life_how_to_do_it_wisely and Lauren Sallan, https://www.ted.com/talks/lauren_sallan_how_to_win_at_evolution_and_survive_a_mass_extinction).

Are newspapers a good source of scientific information?

Generally no. There can be well-documented and comprehensive insights, but the information conveyed by newspapers is typically partial and structured to create so-called clickbait headlines. This translates into a presentation of content geared towards strong and atypical arguments, while overlooking aspects that may be central in the original research. Often the studies cited are not even contextualized, so it is not possible to know if they are prepared by independent institutes or if they are researches that have at least in part originated from contexts that can condition the results themselves (private groups, NGOs, academic institutions, public bodies, etc.).

Should we act immediately?

Yes and no. The principle of urgency should be applied where it is necessary. To say that we must act immediately or that environmental or climate policy is on the brink, promotes a view that carries risks. On the one hand, it tends to conceal the evident steps forward and the concrete results achieved in the last 40 years. Above all, it prevents effective planning of the next interventions. If everything is governed by the principle of urgency, the risk is indeed not to identify those sectors where urgency is real and important.

Should we change the world?

As in the previous question, we must be aware that environmental policy, in recent decades, has achieved positive results. The critical issues are evidently not lacking, but a radical change is not a particularly effective or indicated solution, also due to the possible social impacts that this could entail. Rather than changing, we need to improve and optimize the management of natural resources.

Are the data generally reliable?

Much of the research conducted on the topics covered in this text relies on quantitative methods, measured using usually declared and replicable methods. It is clear that there are studies that can be influenced by external factors or by the bias of the researchers themselves. It can be useful to check who the promoters of the investigations are (academic institute, NGO, government, etc.) and what methodological choices they have adopted. Often statistical analysis techniques come into play that can indeed be used to argue in favor of a thesis (see next question).

Are environmental disasters increasing?

Often in the media, you find numbers and charts attesting to a sharp increase in natural disasters or insurance expenses related to climate events. These are data to be taken with some caution, as growth is not necessarily linked to an increase in the frequency or intensity of natural events. These data indeed conceal other factors (dark data) such as the strong demographic growth of the last century, the drastic increase in built-up surfaces (urbanization) and their respective water refluxes, as well as the overall strong increase in the insured value at the level of built heritage.

Other variables indeed provide opposite indications, such as the average number of deaths caused by natural disasters, which has sharply decreased over the last century (a significant figure in light of demographic growth). Here too, however, it is difficult to establish direct correlations: it is indeed a positive result to which numerous factors have contributed (prevention and intervention systems, consolidation of structures, etc.).

Is human health in danger? Are cancer cases increasing because of our actions?

Based on trends recorded by major indicators, human health is not in danger, on the contrary, the average life expectancy has only lengthened.

As in the case of endangered species, the number of tumors also confronts us with a problem related to the reference population. Demographic growth and access to care by an ever larger slice of the human population have certainly caused a significant increase in registered cases. It should also be considered that technological development has made it possible to better identify different cancer cases.

In addition to demographic growth, with the lengthening of life expectancy, there are more opportunities to develop a cancer case during life.

Like other topics, fear is often used to catalyze change. Is it a good solution?

Fear is a strategy that works very well in the short term, but it risks being counterproductive on other time scales. Linking environmental policies to the "global warming" theme can be risky: as has happened in the past, changes can occur unexpectedly in the complex systems that regulate Earth's autopoiesis. And if the climate started to show contrasting signs, what consequences would there be on policies and public opinion, accustomed to a narrative built on certain predictions? In the long term, it is better to work by focusing on a serious and factually sustainable management of resources, so as to consequently influence the alterations of the systems.

Do climate changes really exist?

Among the few certainties that we can identify, one is this: climate changes do exist, and anyone who denies this is on the same level as flat earthers. Changes in climate systems have always existed, slow or rapid, due to internal as well as external factors. The problem that arises today is to know if and to what extent the ongoing climate changes are influenced by human activities.

Is change synonymous with deterioration?

Clearly, the dominant communication highlights the potential catastrophic impacts of change: this is a dynamic common to other sectors and in some ways hostage to the "good news = no news" model. The reality is less schematic: changes indeed occur with uneven intensity and frequency. This means that in some areas of the world changes will be imperceptible, in others they will have positive impacts and in others still negative.

Can we talk about a Climate Hell or Environmental Cataclysm?

It's difficult to justify the adoption of extreme visions, at least within the context of research texts or with scientific aspirations. It's better to confine such descriptions to post-apocalyptic movies and books.

Are the data on global warming reliable?

The scientific community seems to be largely in agreement: we are facing global warming. However, it should be noted that the climate is a complex system, with resilience and autopoiesis. From this perspective, the data collected today can be used to optimize sectoral public policies. On the other hand, the interpolation towards the future remains problematic, as already seen in many predictions promoted in the past. Finally, there is less certainty about the degree of responsibility of human activities on this trend: from those who consider it limited, to those who consider it total.

Are glaciers disappearing?

Yes, glaciers are disappearing: this is an incontrovertible scientific observation. The few exceptions do not seem to be significant compared to the global trend. Even in this case, the data must be contextualized: choosing different time scales, this decline assumes different values. In past epochs, glaciers could be completely absent or cover large surfaces of the emerged lands: this means that there is no ideal equilibrium condition. The underlying issue concerns the role of man in the last recorded drop: none, limited, or absolute? It's a question to which it is difficult to give a univocal answer.

Are glaciers disappearing because of humans?

The last glacial period, the Würm glaciation, ended roughly between 16,000 and 14,000 BC and began about 115,000 years ago. During this glaciation, vast stretches of Canada, Northern Europe, and Russia were covered by immense ice caps. Due to the formation of these ice caps, a large amount of water was taken from the oceans. This phenomenon led to a significant reduction in sea level, about 120 meters compared to current levels. At the same time, the climate was generally colder and drier than today. It is estimated that average temperatures were 5-10°C lower in areas directly covered by glaciers and 4-5°C lower in tropical regions. These climatic conditions brought about profound transformations in flora and fauna. Many animals, like mammoths, cave lions, and woolly rhinos, thrived in this cold climate, while forests were largely replaced by grasslands and tundra in many regions.

On the European continent, during the peak of the last glaciation, a vast portion of the northern territories was covered by glaciers. Countries such as Great Britain, Ireland, Scandinavia, and parts of Germany, Poland, and Russia were submerged under thick ice caps. This glacial advance left an indelible mark on the European landscape: vast valleys, lakes, and other geographical features, especially in the Alpine and Scandinavian regions, are the direct result of the erosive action of glaciers. The epilogue of this glaciation marked the beginning of an interglacial period, the Holocene, during which we witnessed a milder and more stable climate, creating the ideal conditions for the development of human civilizations as we know them today.

Given this context, it's challenging to support theories that attribute glacier melting to human actions. It's a trend that has continued for tens of thousands of years; the growth of human activities has likely contributed to accelerating and reinforcing these processes.

Is sustainable development synonymous with ecological development?

In many studies, the imperative of sustainability is focused on the ecological component. In the perception of some authors, economy and society are marginal vertices. It should be emphasized that sustainable development aspires to build a human community that lives and works with dignity. In summary, therefore, they are not synonymous: sustainable also means ecological, but not only. Therefore, they are not synonyms.

What relevance should be given to the choice to limit the use of straws?

The plastic straw, after several decades of pervasive use, has undergone a significant reduction in recent years within the broader context of the fight against plastics. Leaving aside the economic and social issues of this rapid change, one might question how actually relevant this product is from an environmental impact perspective. Reading articles appearing in the media, we learn that we are dealing with a huge quantity of straws: 1.6 straws per person per day in the USA, a similar value for Europe. These are estimates that probably overestimate consumption, but they allow us to roughly quantify production. We know that a straw weighs on average 0.4 grams and - wanting to exaggerate - we can estimate a global annual production of 1'153'000 tons of plastic (population 7.9 billion, 1 straw per person per day). In the context of global plastic production, we are talking about 0.25%: in fact, 460'000'000 tons are produced each year (data referring to 2020, OECD Global Plastics Outlook Database). Considering these figures, replacing straws (or not using them at all) is a useful but little relevant gesture. However, it should be borne in mind that - although limited in quantitative value - the phenomenon can become more significant considering its easy dispersion in the environment (like bags and bottles).

Should we give up flying to save the planet? Do airplanes pollute more than other means of transport?

Some issues, like the pollution caused by aviation, are particularly favored by the media and by some schools of thought, a legacy of an era when airplane contrails were blamed for causing global cooling. Today, it is possible to estimate with relative (not absolute!) precision the ecological footprint of different modes of transport: however, it should be noted that this is a complex analysis that can determine very different results, depending on the parameters used (number of passengers per vehicle, type of vehicle, reference year, etc.). For example, extreme results can be obtained by referencing a large-engine car from the 1980s and assuming one or two passengers per trip. Conversely, the energy efficiency of a private electric vehicle, occupied by 4 people, can be better than that of a train with an average occupancy rate. To return to air transport, it is worth emphasizing that it is a sector that overall is responsible for 2% of the global volume of emissions and 12% of those generated by the transport sector.

	Subway at rush hour	Intercity train	Small car (1 or 2 passengers)	Commercial airplane	Suv (1 o 2 passengers)
Energy MJ/pkm	0.1	0.2-0.4	1-2	1.5-2	3-5

Source: Smil, Vaclav. I numeri non mentono: brevi storie per capire il mondo. Torino: Einaudi, 2021.

In some publications, reference is made to the fact that airplane emissions, occurring at high altitudes, are more harmful to the environment. This phenomenon is particularly associated with gases responsible for the "greenhouse effect" global warming. In reality, the causal link is not easy to demonstrate: it seems rather a legacy of the theories related to the ozone hole, where it was believed that emissions at high altitude were more harmful than those emitted at low altitude.

Analyzing the ecological footprint is difficult, especially in light of rapid technological changes and different energy structures between countries: the impact in terms of emissions of means powered by electricity is very different if a nation produces it with coal (India) or with nuclear power (France). Undoubtedly, the narrative promoted by large environmental NGOs based on outdated information and articulated for not always transparent purposes is not constructive.

At the same time, other issues that determine significant impacts but are in fact unpopular and counterproductive in fundraising are not taken into account. A phenomenon that has grown significantly in recent decades, little studied, concerns, for example, the ecological footprint of domestic animals. Or that of mobile phones: 1.75 billion of these objects were sold in 2020. Vaclav Smil, in the book entitled "Numbers Don't Lie", poses this problem in a chapter with an explanatory title: "Does your car or your phone do more harm to the environment?"

In this sense, the statistics concerning the evolution of emissions are explanatory:

Should we be ashamed to fly?

As seen in the previous question, based on the data on impacts, we should not be ashamed to fly. In general, it is better to be wary of those who want to blame or introduce a danger system that judges the behaviors of others. In this case, not only is the aviation sector at risk (responsible, it should be remembered, for 2% of total greenhouse gas emissions), but a large part of the activities that define us as a human community.

More info: https://museumoftravel.org/index.php/en/more/infos/3005-flying-no-shame-in-that-the-airplane-is-a-sustainable-mode-of-transport 

More roads equal More traffic?

In certain areas of thought, it happens with some frequency to hear that the more infrastructure is built (roads, railway lines, etc.) the more traffic they generate. From a purely statistical point of view, it is difficult to support this principle of causality: as in other areas, it seems more appropriate to call into question the socio-demographic factors that are at the root of the problem. It should also be noted that the reference population has increased significantly: this factor alone should make us reflect on the possible repercussions of a block at the level of support infrastructures, whether related to traffic or other distribution networks (water, sewerage, electricity). In summary, therefore, the demographic increase and the increase in the frequency of private and professional movements represent the variables that largely determine the impact on transport infrastructure and traffic.

Is it true that due to humans more and more species are going extinct?

(source: IUNC, 2021)

Based on the work carried out by the IUCN, we can say that the number of species at risk or endangered is increasing, but it is necessary to keep in mind that the reference population is also increasing. In percentage terms, these two variables allow for a decreasing percentage. In other words, the fact that the increase in censused species is more marked than that of endangered species is positive. Considering the still uncertain context, with 93% of species not evaluated, it is still advisable to cautiously evaluate these dynamics, whether they are catastrophic or optimistic.

What are mass extinctions?

In narratives promoted by some organizations, mass extinctions are those caused by human activities. In reality, these specifically refer to five major extinctions that have been recorded in the history of our planet. Over the ages, there have been periods when the extinction rate has been particularly high (at least 75% of species extinct in less than two million years). In the last 500 million years, 5 particularly intense events have occurred:

1. The Ordovician–Silurian extinction event: 443 million years ago
2. The Late Devonian extinction: 359 million years ago
3. The Permian–Triassic extinction event: 252 million years ago
4. The Triassic–Jurassic extinction event: 201 million years ago
5. The Cretaceous–Paleogene extinction event: 66 million years ago

These events have led to the disappearance of between 75% and 96% of all species on Earth. They were caused by massive volcanic eruptions, asteroid impacts, and rapid climate changes. In these contexts, the concept of a sixth extinction caused by human activity appears to be more of a narrative tool than a scientific fact.

Do ecosystems develop linearly?

No, the evolution of an ecosystem is better represented by systemic, complex, autopoietic development. In models, this aspect tends to be simplified, favoring linear developments and the blocking of variables. Another aspect, which plays an underestimated role over longer time scales, concerns randomness. A volcanic eruption, an earthquake, a solar disturbance or another major natural event, can determine changes such as to overturn the previous functioning models.

Which sectors are those that have the greatest impacts on ecosystems?

In general, it is difficult to give an exclusive answer, given the heterogeneity of ecosystems. However, it can reasonably be stated that the sector that shows the most significant impacts is that of energy production (electricity, heating, transport): it accounts for 73.2% of total greenhouse gas emissions. On this front, public policies are intervening by supporting renewable energies, in particular solar and wind, as well as the development of new technologies.

Are there sustainable cities?

Is deforestation still ongoing?

Yes, deforestation is still ongoing, albeit at a lower intensity compared to the past. The rate of deforestation reached its peak during the 1980s, a decade that resulted in the loss of 150 million hectares of forest (like the Amazon rainforest).

Since then, numerous factors have contributed to a rather marked reversal, dropping to 78 million hectares in the 1990s, 52 in the first decade of 2000, and 47 between 2010 and 2020. Temperate forests have for some decades recorded a positive reforestation rate, amounting to 6 million hectares in the last decade: this trend, called the forest transition point, allows us to be optimistic about the future of rainforests.

Are local (zero-kilometre) products more sustainable?

Not necessarily. Transport accounts for only a small portion of the total emissions associated with food production. The environmental impact depends mostly on how a product is grown, not how far it travels. For example, tomatoes grown locally in heated greenhouses may emit more CO₂ than those imported from a region where they grow outdoors and in season.
In some cases, advanced systems such as vertical farms — multi-level structures that optimize the use of water, energy, and space, with continuous and controlled production cycles — can be more sustainable than many traditional farming methods, even if they are not “local”.
Buying local may have other benefits, but it is not in itself a guarantee of environmental sustainability.

10. Sources

Bibliography

Internet