Earth's disturbed ecosystems have much more to offer than many would give them credit for.
Take a look out of the nearest window. Chances are that the view will show a man-made landscape — a residential neighbourhood, a field of wheat, an overgrazed hillside or a weedy forest full of invasive species. An estimated 77% of Earth's ice-free land has now been substantially altered by human activities, and that proportion is likely to rise.
Scientists and conservationists would do well to pay more attention to the landscape outside the window. At the moment, they tend to concentrate on the remote fraction of Earth that looks more or less like it did before humans swarmed the globe, and on the protection of those places. And they have good reason to do so: such relatively pristine sites not only harbour much of Earth's biodiversity, they also offer a unique opportunity to learn how nature works in isolation from Homo sapiens.
Nonetheless, the majority of Earth that is not pristine provides critical support for human life, in the form of agriculture, development and the 'ecosystem services' that sequester carbon, filter water, build soil, shore up hillsides — and it even creates habitats to shelter threatened species.
About half of that 77% of Earth's surface is in direct use by humans for agriculture and urban development. The other half is marked by past human influences — fragmented forests filled with species from other continents, forest plantations, abandoned grazing lands and so on. Some ecologists have begun to classify portions of the latter half as 'novel ecosystems' — areas not currently being managed by people, but so changed by human activities that they have become different ecosystems, with different players and a different trajectory from the system they replaced. Many of these places have changed so much that attempting to return them to their historical condition would be prohibitively expensive, if not impossible, especially with climate change added to the mix. Nevertheless, these alternative states are often species-rich, energetically productive and vigorous providers of ecosystem services (see page 450).
Given these realities, more researchers and conservationists need to expand their interests to encompass urban and agricultural ecologies, as well as novel ecosystems in general. Many have already done so. Next month's meeting of the Ecological Society of America in Albuquerque, New Mexico, plans symposia on soil microbial ecology in sustainable agriculture, agroecosystems of the future and urban design. But such work merits increased support from all of the government agencies and non-governmental foundations that fund ecological and conservation work. A good example is the US National Science Foundation's Long Term Ecological Research Network, which includes among its 26 sites two cities — Baltimore, Maryland, and Phoenix, Arizona — where researchers examine how the human and ecological systems in the city interact and change over time.
Likewise, funders that support research into ecosystem services, such as the US Environmental Protection Agency in Washington DC, should put a special emphasis on anthropogenic areas. Some of these places may even warrant protection, as odd as it might seem to create a park around an overgrown orchard or a lake filled with foreign fish.
None of this is to say that anything goes. Exotic species, pollution and mindless development have wreaked widespread havoc in the past, and strong safeguards are still needed to minimize future damage. Moreover, some novel ecosystems — monocultural stands of invasive plants such as leafy spurge, deserts created by nibbling goats and rabbits or bodies of water devoid of all life larger than algae — are universally considered undesirable and are crying out for intervention and restoration. But not all change is bad. Where a reasonably healthy, reasonably diverse ecosystem is providing at least some kind of service, we might be better off to embrace our altered Earth.
Indeed, when society learns to appreciate ecosystems as they are, rather than always yearning to return to an impossible, pristine past, we may be able to make that 77% work for us so well that we never need to disturb the rest. Preservation of the pristine may depend on our understanding and careful use of the worn and grubby. We may even learn to find some charm there.
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Beyond the pristine. Nature 460, 435–436 (2009). https://doi.org/10.1038/460435b