Planetary boundaries 9 – biodiversity

On week nine of this series, we come to the last of the planetary boundaries – biodiversity loss. It’s a problem that’s fairly familiar to us. Conservation and wilderness preservation were the first environmental causes, so there’s been plenty of time for them to take root in our cultural psyche. And we’re dealing with animals here, and we like animals. We keep them in our houses, visit them in zoos, and watch programmes about them with our children. There’s an emotional connection in conservation that you’re never going to get with the nitrogen boundary.

Unfortunately, that emotional connection is not enough to solve the problem. The number of species going extinct on our watch is high and rising. A quarter of mammals and freshwater fish are endangered, a third of amphibians, and 13% of birds. The fossil record tells us that the earth has witnessed five extinction events in the past, the demise of the dinosaurs being the most famous. The sixth is happening around us, and we have no great volcanic eruption or meteor strike to take the blame. This time it’s us.

While they get the headlines and keep the donations coming in to wildlife NGOs, it’s important not to fixate on extinctions. The final extinction of a species is the technical end of the line, but in terms of ecosystem health, that species may have ceased to play an active role long before. The decline of a species can be serious without causing it to be remotely endangered. Plankton are never going to go extinct, but a 40% decline in plankton numbers has consequences and can’t be ignored. The sharp decline of bees in recent years would be serious whether or not any specific species of British bee became endangered. (As it is, 20 bee species have become extinct in Britain, with a further 35 endangered.)

You can also look at wildlife in the aggregate, the abundance of wild animals rather than the health of individual species. The results are striking. Between 1970 and 2006, the number of wild animals declined by a third. There are a third fewer wild animals today than there were forty years ago. The WWF’s Living Planet Index tracks wildlife numbers across different regions, and the decline is not evenly spread. Tropical wildlife numbers are falling much faster, with some recovery in temperate regions. (The time frame of the graph below flatters the temperature regions. If it covered a 1,000 years rather than 40, you’d see that the recent rise follows an enormous collapse.)


In many ways we’re better off considering these top level facts than the plight of individual species, at least from a planetary boundaries perspective. “It is ecosystems in their entirety that are valuable and irreplaceable as much as the individual species they contain” says Mark Lynas. Biodiversity loss is a planetary boundary because “a healthy diversity of living organisms is essential for ecosystems to function properly.”

That said, ecosystems have a variety of interacting species and they are not all equally important. Of particular importance are the  top predators, because these keep everything else in balance. When you lose a top predator, smaller predators can proliferate unchecked, destroying the populations they feed on, before then dying off themselves. You also get structurally important species, the keystone creatures that support the others. The best example of this is the one I talked about in last week’s post: coral. Thousands of species can thrive in a coral reef – as long as the coral itself is alive and well. Lose that key structural species, and the whole ecosystem will collapse.

How do we manage biodiversity loss? One key aspect is to value nature as nature, and there are a variety of experiments along those lines, the REDD initiatives to protect carbon sinks being the biggest. Wildlife reserves and conservation areas are another way to protect biodiversity, but it is important that these respect the human populations using the land too. Another option is to share techniques that allow people to farm or earn an income within existing ecosystems, rather than clearing them. I wrote recently about layer farming, as one example.

We also need to look closely at the drivers of habitat loss, which are often regionally specific – biofuels and cattle ranching in the Amazon, or shrimp farming in the wetlands of Indonesia. These can in many cases be managed better through incentives and dis-incentives. Biofuel targets, for example, have accelerated land clearance for new plantations, causing considerable ecological damage. More positively, sustainable forestry certification such as FSC or PEFC has gone mainstream.

Restoration of wild areas is another priority. The biggest scale project I’ve come across is probably Africa’s Great Green Wall, which aims to stop the advance of the Sahara desert by planting trees. Britain’s National Forest is a more local scheme, and there are all manner of smaller re-wilding or land reclamation projects around the country, including re-introducing lost species. A couple of weeks ago I visited the forest of Marston Vale, which until the 1950s was home to Europe’s largest brick-works. The smokestacks are mostly gone and the enormous clay pits have been turned into a lake. In another 20 years it will be a forest again.

The authors of the planetary boundaries report acknowledge that “science is, as yet, unable to provide a boundary measure that captures, at an aggregate level, the regulating role of biodiversity.” Instead, they propose the “interim measure” of using the extinction rate, set at 10 extinction per million species per year. We are currently at at least ten times over that rate, so biodiversity loss is in massive overshoot. On this boundary, “humanity has already entered deep into a danger zone where undesired system change cannot be excluded, if the current greatly elevated extinction rate is sustained over long periods of time.”


Boundary: biodiversity loss
Safe limit: 10 extinctions per million species/year
Status:  in overshoot


One Comment on “Planetary boundaries 9 – biodiversity”

  1. john taylor August 9, 2013 at 10:25 am #

    Very interesting report- worlds population continuing to increase will infuse its own problems on our planet-certainly the UK /England is very much over populated now around 70million, & with this rapid increase the need for housing, utilities to sustain this housing is another major destructive factor to be put upon surrounding nature.

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