The entangled bank unravels

    This third special issue in Nature's year-long celebration of Charles Darwin focuses on the dire challenges to Earth's biodiversity — and finds some reason for hope.

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    “It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth.” So Charles Darwin begins the concluding paragraph of On the Origin of Species, published 150 years ago next week. By invoking this gentle image, Darwin sought to emphasize how “endless forms most beautiful and most wonderful” have all evolved through the process of natural selection.

    Were he alive today, Darwin would have cause to be less rhapsodic. The modern version of his bank might well be dominated by invasive shrubs, having been denuded of most native plants by deforestation, and nearby streams would probably be polluted and filled with sediment from excess run-off.

    It is hardly news that the rich pageant of life, which inspired Darwin and his work, is now suffering. According to data released this month by the International Union for Conservation of Nature in its Red List of Threatened Species, one-fifth of mammals and nearly one-third of amphibians are threatened with extinction, and the situation is no better among plants: almost one-third of known gymnosperms, the group that includes conifers, are threatened. Yet despite all the warnings from scientists and environmentalists, nations have done little more than fret over the problem. Although almost 200 countries have pledged through the Convention on Biological Diversity to significantly reduce the rate of biodiversity loss by next year, leaders of that effort acknowledge not only that the world will come up short of this target, but also that it was basically unachievable from the start and that it represented more of a political statement (see page 263).

    This week, Nature ends its year-long celebration of Darwin ( by examining some of the most pressing issues concerning the loss of biodiversity, as well as ways to address the problem. The fact that upper levels of government are beginning to focus their attention on the biodiversity crisis gives some cause for optimism. For example, the United Nations General Assembly has named 2010 as the International Year of Biodiversity, with a meeting scheduled in New York next September at which heads of state will take up the issue. The following month, parties to the biodiversity convention will gather in Nagoya, Japan, to develop specific and verifiable biodiversity targets for nations over the coming decades. These meetings give countries an incentive to start protecting vital ecosystems during the next 11 months so that they can head to the Nagoya summit boasting of success.

    There is growing recognition that diverse ecosystems can provide substantial economic benefits — a concept known as ecosystem services — which has strengthened support for conservation in the business and political communities. The News Feature on page 270 profiles ecologist Gretchen Daily of Stanford University in Palo Alto, California, an advocate of this concept who helped it to emerge as a major idea in conservation. Another article (page 266) shows this concept in action in Brazil, where it has helped to preserve the remaining patches of the species-rich Atlantic forest. And in an Opinion piece (page 277), the leader of an international study, known as the Economics of Ecosystems and Biodiversity (TEEB) project, argues that governments must put taxes and benefits in place to protect nature's 'public goods'. Just last week, the TEEB project announced initial results suggesting that investments in conservation can reap economic benefits that far exceed the initial outlay.

    The situation in Brazil is a good example. Preserving patches of forest has not only helped the golden lion tamarin to survive, but has also helped to provide clean water, flood control and other economic benefits to nearby communities. These 'win–win' situations are natural starting points for conservation efforts because they are easily sold to politicians and other stakeholders.

    Climate change will place new stresses on already weakened ecosystems but it can also present political and economic opportunities. One example is a strategy known as reducing emissions from deforestation and forest degradation (REDD). According to estimates by the Intergovernmental Panel on Climate Change, the clearing of forests accounts for approximately one-fifth of greenhouse-gas emissions by humans. Thus, stopping deforestation could be a relatively cheap and effective way to reduce emissions and slow the rate of global warming. At the same time, argue Will Turner and his colleagues in an Opinion piece on page 278, efforts to preserve natural ecosystems can help to ameliorate some of the effects of climate change. The international climate treaty currently under negotiation is likely to include a REDD mechanism that would provide funds to tropical countries to save their forests, a move that would help to mitigate climate change and sustain biodiversity.

    Although ecosystem degradation looks set to increase in the future as a result of climate change, the biggest threat to biodiversity today is the rapid disappearance of habitats. At present, only around 14% of land surface and less than 6% of territorial seas are protected worldwide. Yet such areas help to support nearly one-sixth of the world's population, according to the TEEB study. As nations look beyond the likely failure of the 2010 biodiversity target, they should commit to placing more areas under protection. It will be crucial to select valuable sites that harbour the species that are most threatened. The wealthiest sectors of society tend to be the most removed from nature, whereas the world's poorest people rely heavily on the fruits of diverse ecosystems. As a result, care must be taken to ensure that conservation initiatives do not come at the expense of people, particularly indigenous communities that can be indirectly harmed when land is suddenly set aside.



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    The entangled bank unravels. Nature 462, 251–252 (2009).

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