Specials
Extinction or conservation?
Generally there are two differentiate extinction typologies. There are “long distance” extinctions which correspond to a slow and imperceptible alive world tendency to constantly change into other things. Then there are “episodic” extinctions, that reflect a big quantity and concomitant specie deaths that are caused by fast environment alterations.
In general, the extinctions who mostly contributed to flora and fauna drastic mutations were caused by the second type. A few extreme events that were proved on large scales during the geological eras, such as climate changes or asteroid and comet impacts with our world, caused radical environmental perturbations and this killed many organisms. In different moments of Earth’s history, these phenomenon represented severe limited factors for species survival, causing then less biodiversity of entire geographic regions and bringing up to “mass extinctions”.
The 5 historic mass extinctions
- 430 million years ago (Upper Ordovician), specie number reductions of 84/85%
- 360 million years ago (Upper Devonian), specie number reductions of 79/83%
- 250 million years ago (Permian), specie number reductions of 95%
- 200 million years ago (Triassic), specie number reductions of 79/80%
- 66 million years ago (Upper Cretaceous), specie number reductions of 70/76%
In pure ecological terms, the extinction cause of a specie is their habitat destruction and the impossibility to find another one. When there is a big change within physicals and chemicals characteristics with an excessive rapidity compared to the biological adaptation time, the organisms that live there die, unless they are able to migrate.
The five big biological extinctions of the past were caused by ecological dynamics that don’t depend on human impact (for the fact that homo sapiens appeared considerably later on) that used to have the same characteristics. For example, biologists retain that both extinctions of the upper Ordovician and upper Devonian have been the result of a violent weather condition mutation, whilst they sustain that the upper Cretaceous’ extinction was caused by a collision between our planet and one or maybe two big meteorites: it is well known these collisions had such backlashes on the biological balances determining the dinosaurs and many other organisms disappearance.
In this moment though our planet is experimenting a fact that never happened in the past: a very quick specie disappearance caused by man. According to scientists today’s erosion speed of biodiversity is comparable to the one that characterized the big extinction events of the past, with one difference only which is caused by human activities.
Beyond obvious ecological implications, we have to do with a process which assumes an ethical and cultural valence that can’t be balked, differently from what was confirmed about the 5 big historic extinctions. Many times we ask ourselves if it is right that man can dilapidate the biological richness of the planet without thinking about his responsibilities for nature’s survival and for the future human generations. According to many authors the “ecological crises” we are living might have negative consequences on our life quality in very short time, and it is obvious that this preoccupation might give reflections and discussions not only from a scientific point of view.
There are different modalities in which man is responsible for other species disappearance. From this point of view the fundamental responsibility is the agriculture impact on the ground ecology. The agricultural ground conversion to meadows and humid environments by subtracting huge surfaces from the forests, deeply simplified the ancient biomes and ecosystems structure. Naturally these alterations had different outcomes in extinction terms: in the tropical and subtropical belts, where biodiversity reaches the highest values, the agricultural conversion results of the ground have been worse than in higher latitudes. Industrialization and urbanization played a fundamental role in the species extinctions. In particular in the past three or four centuries the human demographic growth registered a tax that has never been reached in the past and deeply modified the physiognomy and the ecology quality of the habitats by the cementing industrializing natural environments. Another crucial factor in the actual biodiversity loss is the anthrop climatic change. The greenhouse gasses accumulation in the atmosphere emitted by man caused in fact a global temperature increment which gave heavy biological alterations in many planet regions with documented extinctions phenomena.
The extinctions origin that have been registered till now isn’t very recent. Man caused the extinction (directly or indirectly) of many different kinds of animals and plants since 400 years ago. It must be taken into consideration that many species can survive thanks to captivity breeding or to conservation programs.
Documented extinctions since 1600 till today
Mammals - Ascertained specie extinctions 85, Percentage of extinct species 2,1%
Birds - Ascertained specie extinctions 113, Percentage of extinct species 1,3%
Reptiles - Ascertained specie extinctions 21, Percentage of extinct species 0.3%
Amphibious - Ascertained specie extinctions 2, Percentage of extinct species 0,05%
Fish - Ascertained specie extinctions 23, Percentage of extinct species 0,1%
Invertebrates - Ascertained specie extinctions 98, Percentage of extinct species 0,01%
Angiosperms - Ascertained specie extinctions 384, Percentage of extinct species 0,2%
The IUCN organisation (International Union for Conservation of Nature and Natural Resources) systematically elaborates a “red list” of the menaced organisms of extinction that actually are 12.500 species divided into three categories such as “critical danger”, “in danger” and “vulnerable”. More than 1000 up on 10.000 bird species, for instance, are grouped in one of these three categories up above, which means that more than 10% of the world’s avifauna is risking to be extincted.
Vertebrate Species menaced of extinction
- Mammals - 4.500 number estimation of species and 505 menaced species (black rhinoceros, tigre and other felines, African elephant, gigantic panda, gibbon from Giava, many canines and deer, hedgehog and other rodents, marsupials)
- Birds - 9.500 number estimation of species and 1.029 menaced species (kestrel from Mauritius, Philippine eagle and other raptors, Spix ara and other parrots, American crane, ducks, geese, swans, swallows)
- Reptiles - 6.000 number estimation of species and 167 menaced species (lizards, boa, monitor, turtles, iguanas)
The problem can assume a more alarming connotation. In fact, if it is possible to monitor easily the organisms at risk on one hand and so it is possible to use efficacy measurements for their protection, on the other there is an entire organism universe that isn’t so easy to keep an eye on because they might be microscopic, they might have certain habits, or probably they haven’t been discovered yet, so they are able to escape from every evaluation on their conservation estate. It is important to emphasize because probably most of the planet’s biomass is concentrated in these organisms, that play an indispensable role in the ecosystem’s balance.
To realize the weight our specie influences on the global ecosystem, it is supposed to be considered the entire area of the planet which is 51 billion hectares. The emerged earth occupies a bit more of 14 billion hectares of this surface that according to FAO (Food and Agriculture Organisation) this is supposed to be furthermore divided into:
- 2 billion hectares of cultivated and edified areas;
- 3,4 billion hectares of permanent pasturages and meadows;
- 3,8 billion hectares of forests and woods;
- 5 billion hectares of icy soil, tundras, deserts and humid environments.
Evidently we have to count on the unoccupied surface for food production, for using and extracting resources and for the human rubbish relieve. This is an obliged step to do because our planet has an adequate surface and the a capacity to produce resources, but they aren’t endless.
It has been calculated that humanity has 2,3 hectares of bioproductive territory a head (an average quote of earth to obtain food) related to the actual demographic pressure level, including the cultivated and farming areas fraction and the oceanic surface fraction necessary for fishing. It has been observed though that 2,3 hectares estimation considers our specie exigents only and ignores the necessity of the others. Taking into consideration these exigents too, and crediting the United Nations’ forecasts which was said that in the year 2050 the human population will reach 10 billions of people, it has been seen that the bioproductive territory will be lower than 1 hectare a head. The question is: will this surface be enough to guarantee man’s survival without compromising furthermore the planet’s biodiversity?
From extinction to conservation
There is at this point an evident risk for the planet’s biodiversity, and is also evident that there cannot be just a scientific answer because there must be a cultural one too. After all, if we think about the role of the biological patrimony for man’s survival, it is possible to intuit how much the biological conservation is important and it involves institutions and agencies of the World.
The most important step ever realized until today to formally seal the necessity to conserve the natural patrimony is the international concordat know as Convention on Biodiversity (CBD).
The agreement has been signed in 1992 from 156 states (the European Union too), during a Conference on Environment and Development organised by UNO (United Nations Organisation) in Rio de Janeiro, and fixed a principle which specifies that biodiversity is patrimony of all the humanity, so it has to be used according to ecological sustainability rules and social equity between every population of the world.
The conservation concept as worthy theme to the international attention is anyway previous the CBD. The first attempts, in the past century, to understand better this problem and to manage in a rational way brought up to foundations of many prestige organisations, such as WWF (World Wide Found for Nature) and many others. High qualified experts on environmental social and economical themes, work in these organisations.
Conservation became more than an exclusive matter of scientific pertinence: it became a matter that needs to be solved with right measures which go from economy to law, from social sciences to natural sciences, from philosophy to biomedicine, and so on. Experts noticed that extinctions and other erosion types of biodiversity can be faced with instruments that are at our disposition thanks to different fields of knowledge.
What appears more necessary is a different way to think about the relationship between man and nature: a challenge that can’t be faced with one type of knowledge only
written by Carlo Modonesi
