多样性减少，给人类带来了什么危害

If aspeciesof bee disappears forever or a particular plant is extinct, what does it have to do with us humans? Well, according to a team of international scientists, biodiversityis dropping below levels considered safe for the wellbeing of human societies.

The issue is that everything is interconnectedand ecosystemssupport our societies because they provide us with, for example, food, fibres and fuels.

If species go on disappearing, this can interferewith vital processes such as crop pollinationand thedecompositionof waste.

A frameworkwhich defines the environmental limits within which humans can operate – calledplanetary boundaries- says that losing more than 10% of the biodiversity in an area places the local ecosystem at risk. Ecosystems are all different but this percentage is considered a good measure of safety.

A study published in the magazine Science suggests that 58% of the world's land surfacealready falls below this level. These areas house 71% of the global population.

Professor Andy Purvis, from Imperial College London and the Natural History Museum, is one of the authors of the study. He says: "Once we're the wrong side of the boundary it doesn't mean everything goes wrong immediately, but there is a markedly higher risk that things will go badly wrong."

The researchers found that grasslands, savannasand shrub landswere most affected by biodiversity loss on average.

Purvis hopes this report can be a wake-up call to those who design policies. Here's his warning: "Decision-makersworry a lot about economic recessions, but an ecological recession could have even worse consequences – and the biodiversity damage we've had means we're at risk of that happening. Until and unless we can bring biodiversity back up, we're playing ecological roulette."