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Thursday, June 14, 2012

Bad news for biodiversity and humankind

It has been known since the 80’s that removing a single species (aka extinction) from a biological community can have profound effects on that ecosystem. But just how closely are biodiversity (a measure of the variety of species) and healthy ecosystems linked? To answer that question, Bradley Cardinale from the University of Michigan and 16 other authors from institutions in the U.S., U.K., Canada, Sweden and France reviewed two decades of research on biodiversity and its effect on local and global ecosystems.

Among their findings are the following:

The rate of conversion of resources (be they photons, plants or prey) into new biomass suffers as biodiversity decreases. In other words, fewer species means less food, fiber and other products. Other natural processes, such as decomposition and recycling, also decline as species number goes down.

It's a combination of the presence of specific key species and the total diversity that makes an ecosystem productive. You need both.

And perhaps most sinister: the change is nonlinear. That is, as you lose biodiversity, the rate at which that loss impacts our environment speeds up. Add to this the fact that the rate of species loss has been steadily increasing, and you have a crisis in the making.

In fact, another international study led by Anthony Barnosky of the University of California, Berkeley and Elizabeth Hadly from Stanford University suggests that we may already be at a tipping point of irreversible change. According to the 22 authors of that study, our present rate of climate change exceeds that seen at any time since the end of dinosaurs.

It’s not only carbon emissions that matter though, but land use as well. Once somewhere between 50-90% of an area has been altered (as for farms or cities), that region can no longer support the original ecosystem. As of right now, about 43% of the Earth’s total land surface has been completely modified for human usage. That percentage is expected to increase to 50% by 2025.

The authors recommend that governments take immediate action to forestall the coming catastrophe. In particular, they insist that the Earth’s nations:
Reduce world population growth and per-capita resource use, replace fossil fuels with sustainable sources, develop more efficient food production and distribution without taking over more land, and better manage the land and ocean areas not already dominated by humans as reservoirs of biodiversity and ecosystem services.
Unfortunately, I put the chances that my government (the U.S.) will agree to these actions at somewhere between zip and null. However, there’s a United Nations Earth Summit planned for June 20-22 in Rio de Janeiro, Brazil to discuss biodiversity and climate change. Perhaps something can be accomplished.

Image caption: The Earth may be approaching a tipping point due to climate change and increasing population.
Credit: Cheng (Lily) Li.