The God Species: How Humans Really Can Save the Planet.... Mark Lynas
not because killing off species is morally wrong, but because a healthy diversity of living organisms is essential for ecosystems to function properly.
Living systems keep the air breathable and water drinkable for themselves and us, but to continue to perform these vital services they need to retain their complexity, diversity and resilience. Once humans start to pick off component parts, an ecosystem may appear to function as normal for a while – until some unpredictable tipping point is reached, and collapse occurs. Conceptually this is a bit like the game of Jenga, where wooden blocks are built together in a tower and pieces removed from underneath one by one by each player. Needless to say, whoever removes the crucial ‘keystone’ piece that topples the tower loses. The lesson of Jenga is an important one, because it shows that there is no single keystone: each removed block makes the tower less and less stable, but no one knows in advance which piece will lead the tower to collapse.
Keystone predators are particularly important to ecosystems. In the marine realm, great sharks – like tiger, hammerhead, bull and thresher sharks – have in recent years been mercilessly targeted worldwide: their numbers have plunged by up to 99.99 per cent in some seas.38 On the eastern North American coast, rays are no longer being eaten by the vanished sharks, and have increased their numbers as a result. They in turn eat scallops and oysters, destroying the formerly productive scallop fishery.39 The process is known as a ‘trophic cascade’ and is now understood to be a fundamental part of ecological dynamics. An ecosystem shift can be irreversible: the Newfoundland cod, whose numbers collapsed because of overfishing in 1992, are unlikely ever to return in substancial numbers. Cod larvae are eaten by smaller fish and crustaceans like lobsters (once kept in check by more numerous adult cod), which dominate the ecosystem instead.40
For land-based ecosystems apex predators are just as important. In Yellowstone, the reintroduction of wolves in 1995 has allowed the regrowth of native aspen trees for the first time in half a century. This is because elk populations are now being controlled by wolf predation, preventing overgrazing and allowing trees to recover.41 In nearby Grand Teton National Park in Wyoming small birds like the gray catbird and MacGillivray’s warblers may depend for their survival on wolves, recently reintroduced to the area after an absence of 75 years. Both birds flourish in riverside willows: but the willows, like Yellowstone’s aspens, were being overgrazed by hungry moose. In places where predators are still absent, expensive management schemes have to artificially keep down the populations of deer and other grazing herbivores – a service that wolves perform for free.
However, it is not only predators that count. Bottom-up interference can also dramatically destabilise an ecosystem. In the early 1980s a new pathogen appeared in the Caribbean near the mouth of the Panama Canal, wiping out sea urchin populations with extraordinary virulence: within a year 98 per cent of the urchin population was gone, in what is still the worst recorded die-off of any marine animal in history. Because urchins are herbivorous grazers they perform an important function on reefs, keeping the corals clear of algae and seaweed that would otherwise choke the reef systems. Without them, the corals lacked protection, and within a year reefs from Jamaica to the coast of Venezuela disappeared under a thick layer of green slime.42 After a decade, just 5–10 per cent of the original coral cover was left,43 and little more remains to this day.44 A whole marine ecosystem had irreversibly collapsed because of the removal of one of its key components.
Functioning ecosystems need not just a varied number of species, but also – just as crucially – habitat. Humans have disturbed, fragmented or ploughed up huge areas of the planet’s terrestrial surface. But there is a direct correlation between biodiversity and land area: the smaller the remaining fragment, the fewer species it can support. This so-called ‘species–area relationship’ was illustrated by a massive – though unintentional – field experiment beginning in 1986, when a gigantic hydroelectric dam was built in the jungles of Venezuela. When the lake behind the dam began to fill, the rising tide turned a hilly area of four thousand square kilometres into isolated islands, each with its tropical forest plant and animal species cut off by the surrounding waters. Some of the new islands were very small, just an acre or two in size, whilst others were relatively large, with areas of 150 hectares or more. As you might expect, the smallest islands lost the most biodiversity – three quarters of their original complement – due to their small areas. All islands, large and small, lost their top predators: the jaguar, puma and harpy eagle. But the species that did survive quickly became more abundant as both competition for food and predation ceased abruptly. Some islands were overrun by leaf-cutting ants. One, having housed a large herd of capybaras as the waters rose, ended up as little more than bare ground covered by capybara dung. On some islands, monkeys decimated bird populations, whilst on others rodent populations increased 35-fold.45 In all cases, complex and formerly diverse ecosystems were torn apart and thrown into chaos.
From these and many other examples, ecologists now understand a fundamental principle of biodiversity: that the greater the diversity of species, the more resilient and stable an ecosystem can be. The same, of course, applies to the biosphere as a whole. We are only just beginning to realise all the myriad ways that different species act unconsciously together to keep this planet habitable and its climate tolerable. Might there be some kind of global ‘tipping point’ – like the ones that were passed in the Newfoundland cod fishery and the Caribbean coral reefs – where some kind of irreversible global ecosystem shift takes place? This is the possibility that the planetary boundary on biodiversity is intended to prevent: it is now absolutely clear that the Earth’s living biosphere depends fundamentally on the maintenance of a broad level of species diversity. If the Sixth Mass Extinction is allowed to continue – or still worse, accelerate further – then the chance of a global-scale ecosystem collapse can only continue to grow. the price of pandas
The current crisis in biodiversity tells us loud and clear that conventional approaches to conservation have failed. ‘Paper parks’ – named but barely protected – in developing countries are routinely violated by poachers and loggers. What areas are set aside for nature reserves are too small and too fragmented. At sea fishermen compete with each other in a global race to the bottom, knowing that if they do not catch the last bluefin tuna, someone else will. No wonder the 2010 Global Biodiversity Outlook report is full of ominous words and phrases like ‘serious declines’, ‘extensive fragmentation and degradation’, ‘overexploitation’ and ‘dangerous impacts’. To meet the planetary boundary, we need to make urgent changes in policy.
Biodiversity loss is fundamentally an enormous market failure, because the people that profit from destroying biodiversity are not generally the same people who lose out when the rainforests, mangroves and coral reefs are finally gone. When palm-oil companies move into the last remnants of rainforest in Borneo, the biofuels they sell deliver benefits to shareholders and foreign consumers, but local people are the losers, as are all the rest of us because of the destructive impact on the world’s climate and ecosystems. Our chief task today is to design systems that value nature in a direct and marketable sense and deliver hard cash to those who are in a position to protect ecosystems in a reasonably intact state. What is needed is not more moralising, but more money.
This kind of talk makes many environmentalists queasy. Greens generally view biodiversity conservation as a moral cause, and any discussion of financial mechanisms and marketing schemes arouses strong and principled opposition. Why should any other species, each with just as much right to occupy this living Earth as us, be forced to ‘pay its way’? This objection is understandable but wrong-headed: what I am proposing is not a liquidation of nature to make money, but using money simply as a convenient means to safeguard its protection. Money is a measure of value: put a price on wild animals and plants and we will put a value on them too. This is a pragmatic strategy, only to be used in desperation because the others have failed.
But