Editorial: 鈥�Biodiversity: Keep fighting the good fight鈥�
THERE is a future out there 鈥� not in a parallel universe but right here in this one 鈥� in which the inexorable decline of wildlife and rise of global temperatures are both stemmed. For the first time we have a tool that can tell us how.
That tool is a 鈥渘ature in a box鈥� model, capable of replicating the minute and complex ways in which ecosystems respond to human meddling. We can visualise just how much damage humanity has done to Earth鈥檚 biodiversity so far, and play the model forward to see how wilderness will change with time. Better still, we can test solutions and build tailor-made fixes to stem the persistent decline in biodiversity, and the rise in global temperatures as well.
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So, short of culling humans, how do we stop destroying biodiversity? Earth鈥檚 ecosystems certainly need help. Species are vanishing at rates orders of magnitude higher than normal. Populations and ranges are shrinking, mostly because cities and farms are taking over. Yet we depend on these diverse ecosystems for survival. Insects pollinate crops, , and plants suck carbon dioxide from the air and store it, damping down the greenhouse effect. 鈥淭he biosphere is the reason we are not in a catastrophic climate state already,鈥� says of the Stockholm Resilience Centre in Sweden.
The new model was built by an international group of ecologists belonging to the . The team has gathered data from over 10,000 ecosystems in 64 countries, offering snapshots of a huge range of habitats, the species that live there, and how they respond to humans. They focused first on species richness 鈥� how many species were sampled at each site 鈥� to get a simple indication of a site鈥檚 biodiversity. As one might expect, wilderness habitats like rainforest are the most species-rich. Converting them to cities, croplands and pastures culls up to 45 per cent of the .
The Predicts team calculates that ecosystems are on average 16 per cent less rich in species than they were 500 years ago. Europe, the US corn belt and the up to 40 per cent of their species richness, largely due to intensive farming (see map), according to results presented by Tim Newbold of the World Conservation Monitoring Centre in Cambridge, UK, at the .
Given the apocalyptic picture so often painted of biodiversity loss, a 16 per cent fall in species richness might sound OK. But Predicts team leader of Imperial College London disagrees. 鈥淚f you were in a plane and were told you鈥檇 lost 16 per cent of the parts since you took off, how happy would you be?鈥�
The fact is, we don鈥檛 know how much biodiversity we can lose before vital services provided by healthy ecosystems decline dangerously, or stop entirely. 鈥淎ll we know,鈥� says Rockstr枚m, 鈥渋s that species richness is good.鈥� He recently proposed that we should aim to keep at least 70 per cent of the species in every ecosystem (). 鈥淲e are halfway to failing that,鈥� Purvis points out.
The Predicts team has forecast how much more could be lost this century. They modelled four possible futures 鈥� called the Pathways (RCPs) 鈥� which were initially developed to forecast climate change, and range from rapid emissions cuts to exorbitant fossil fuel use. They include assumptions about how land use will vary: turning wilderness into farms means more greenhouse gases end up in the atmosphere.
In all four scenarios, species richness fell. But in one, dubbed , the decline virtually halted by 2100. Drilling into the results revealed this was because farmed land decreases under RCP4.5.
Farms damage ecosystems, and conservationists have long debated solutions. Farms can become wildlife-friendly, but that cuts yields and means farms must expand. Or they can become more intensive 鈥� the farm itself becomes a biodiversity desert, but more land is left wild elsewhere. Controversially, the Predicts model suggests intensive farming might work best.
The trouble is that an RCP4.5 future would raise global temperatures between 2聽掳C and 4聽掳C above pre-industrial levels 鈥� over the 2聽掳C 鈥渄anger threshold鈥�. An alternative scenario, , keeps global warming below the threshold, but does nothing for biodiversity.
So neither scenario is ideal. 鈥淚 wouldn鈥檛 want to live in either,鈥� says Newbold. 鈥淩CP4.5 sounds pretty good, in terms of land use and biodiversity, but if it results in a 4聽掳C rise I don鈥檛 think I鈥檇 go for it.鈥�
Nobody had predicted a conflict between climate change and biodiversity, says of the Institute of Zoology in London. But he says there need be no trade-offs. 鈥淲e need to identify alternative 鈥榳in-win鈥� land-management models.鈥�
According to Rockstr枚m there is an obvious starting point: farmland, which slashes biodiversity and aggravates climate change by removing valuable carbon storage. 鈥淭he only way is to decide that we鈥檙e not going to feed the world by expanding agriculture,鈥� he says. 鈥淲e鈥檝e gone through 8000 years of agricultural expansion, and we need to recognise that this is it.鈥�
鈥淭he only way is to decide that we鈥檙e not going to feed the world by expanding farmland鈥�
Ultimately, he goes on, the solution is to set a price on carbon emissions, and make it possible to buy and sell the amount of carbon stored in ecosystems. That would make it costly to destroy wild lands, providing an economic incentive to preserve them and shrink farms. Such a system goes far beyond existing carbon markets, which only include emissions from power plants and industry, but Rockstr枚m says it is the logical endpoint. 鈥淔ocusing on fossil fuel emissions only takes us about halfway [to stopping climate change]. We have to go full-on.鈥�
He insists that it is possible to save both the climate and biodiversity. In Predicts, says Purvis, we now have the tools to design and test a future that would offer the best of both worlds, packaged into one.
This article appeared in print under the headline 鈥淭he best of all possible worlds鈥�
