Nickel mining in New Caledonia has severely eroded the upper parts of certain massifs
and has had a devastating impact on the environment.
|
It should not be believed
that all beings exist for the sake of man. On the contrary, all other beings too
have been intended for the sake of something else.
Moses
Maimonides,
theologian, Jewish philosopher
and doctor (1135-1204)
|
 |
How ecosystems work and
what part they play in biodiversity remain a mystery. But we do know that they perform
a host of invaluable services for the human species
 In my view, biodiversity’s fundamental
value is neither aesthetic nor economic but environmental, even though most people
are largely unaware of this. The value of biodiversity is often measured in terms
of the number of species living in a given area. But the interactions between the
many species in an ecosystem, and between them and the environment’s physical and
chemical components are also very important. This highly intricate web of relationships
makes an ecosystem more valuable than the sum of the species it contains.
Ecosystems perform services that are essential for the survival of the human species.
They fix carbon in the atmosphere and produce oxygen, protect soil from erosion and
keep it fertile, filter water and replenish aquifers, provide pollination and anti-parasite
agents and so on.
The first two of these services are closely related to each other. They result from
photosynthesis, whereby green plants, starting with algae, absorb carbon dioxide
(CO2) and emit oxygen. For millions
of years, the balance between the various gases in the atmosphere remained stable.
But with the coming of the industrial revolution, humans began burning increasing
amounts of fossil fuels. Today, three billion tonnes of carbon build up in the atmosphere
each year, and natural ecosystems can no longer absorb all these emissions–especially
since they are disappearing at an alarming rate. Deforestation alone releases such
tremendous amounts of CO2 and other gases, such as methane,
that it has become the second-leading cause of global warming.
Storing freshwater, protecting soil and keeping it fertile are three other closely
related functions. Ecosystems are veritable “freshwater factories”. They absorb rainwater
and slowly filter it through the soil before draining it towards streams, rivers,
lakes and underground aquifers that supply us with the precious liquid. When the
vegetal ground cover is degraded, the water cycle is disrupted. Rain strikes the
bare earth, washing away huge amounts of nutritional substances. Reservoirs, lakes
and rivers silt up and terrible mudslides, such as those that recently ripped through
Central America, Mexico and Mozambique, kill thousands of people and cause incalculable
damage.
Uncertain
reaction to climate change
Despite years
of research, scientists still know very little about how ecosystems work. We are
generally incapable of predicting how they will react to certain transformations
in the environment, especially climate changes. Nor do we know any more about whether
a species present in a given environment is superfluous or “replaceable”, even when
it is very rare. Likewise, we do not know which key species are indispensable to
maintaining an ecosystem, with a few exceptions such as pine forests, where that
tree is obviously the dominant species.
We know even less about the part biological diversity itself plays in maintaining
ecosystems and the services they perform. One simple example is a highly diversified
forest that absorbs carbon dioxide–a vital function, as we have seen, for limiting
global warming. Suppose the forest is cleared to make way for a single-crop forest.
The service will still be performed, perhaps even better at first because young,
fast-growing trees absorb more CO2 than old ones, which regenerate
slowly. But what will happen in the long term? After several decades, the consequences
of the loss of biodiversity will probably be felt. Replacing many species with a
single one will have certainly depleted the soil and, in the long term, slowed down
the forest’s growth and consequently its ability to absorb CO2.
More generally, diversified ecosystems seem more productive. Specialists remain wary
about their conclusions, but today they believe that biodiversity helps ecosystems
to resist alien species and diseases and to recover faster in the event of disruption.
In the face of doubt, and to find out more about them, it is better to preserve as
many different ecosystems as possible.
A
costly lesson for New York City
Most people
take it for granted that ecosystems will carry on performing services without receiving
anything in return. They think nature will continue benefiting humanity, no matter
how much damage is done. The survival of organisms other than our own species is
perceived as a frill that future generations can live without.
These preconceived ideas are wrong and dangerous, as the city of New York has recently
come to realize. The city’s water has always enjoyed such a good reputation that
it was sold throughout the northeastern United States. Its quality was due to the
Catskill Mountains’ natural purification system. But that ecosystem has suffered
so much from pollution, especially fertilizer run-off from farms, that by the late
1990s New York’s water had become undrinkable. The city planned to build a purification
plant, whose cost was put at between six and eight billion dollars, not including
the $300 million in yearly operating costs–an astronomical bill for a service that
had always been free! The price was so staggering that the city eventually decided
to restore the Catskill Mountains’ degraded environment at a cost of only one billion
dollars.
This story clearly illustrates where our interests lie. We must preserve ecosystems
and the conditions that enable our planet to ensure the survival of Homo sapiens
or, at least, the short-term maintenance of our current quality of life.
|
