Rainforests doomed unless world adopts ‘development without destruction’, warn scientists

Tropical forests face a dire future unless humans adopt a radically different approach to protecting and managing them, warns a review published last week in the journal Science.

The paper, published as part of a special series on global forests ahead of climate talks to be held in Paris, provides an overview of the past, present and future of tropical forests, including laying out the familiar pathway by which people transform diverse natural ecosystems into ecological wastelands.

The path begins with selective logging, which opens up intact forest landscapes to hunters and additional impacts. Once the valuable timber has been stripped from the forest, specialist logging companies give way to generalist loggers that less discriminately harvest wood. Once timber stocks are depleted, concessions may be turned over to industrial plantation developers or agribusiness, which convert degraded — but still natural — forest for oil palm, rubber, soy, or stands of monoculture hardwoods. Or the land is stripped completely for cattle pasture, urban areas, or mines. Growing human population and affluence is increasing demand for raw materials and commodities produced in the tropics.

Another trail toward degraded landscapes is blazed by subsistence farmers, who follow roads that bisect forest areas or nibble away at the edge of forests for small-scale agriculture, ranging from maize to oil palm. The fate of these plots depend on local conditions — they may be sold to commercial commodity producers in high deforestation regions linked to broader markets or abandoned and left to return to forest in remote, unconnected areas.

The first cut also leads to more subtle changes, including the influx of hunters and invasive species that affect the local ecology and resilience. Fragmentation triggers edge effects that dry the forest and increase its vulnerability to fire, a phenomenon that is typically rare in most tropical forests.

At the same time that these changes are occurring, tropical forests are facing uncertain impacts from climate change. While some research indicates that rising carbon dioxide levels are spurring increased carbon uptake by tropical trees, some of this gain is offset by the effects of higher temperatures and diminished rainfall. These effects can be complicated or exacerbated by land use change, which shifts the albedo of Earth’s surface, or smoke from fires.

These trends and changes raise serious concerns about the state of tropical forests toward the end of the century, say the authors, led by Simon Lewis of University College London.

“By the end of the century, the world’s remaining tropical forests will be left in a fragmented, simplified, and degraded state,” Lewis writes in a post in The Conversation. “No patch will remain untouched – most remnants will be overrun by species that disperse well, which often means ‘weedy’ plants like fast-growing pioneer trees and small rodents that thrive in disturbed areas. Most of the rest will be “the living dead” – tiny remnant populations of plants and animals hanging on with no future.”

But that fate is not set in stone, the authors argue, pointing several opportunities to change course on forests.

First, argue the authors, humanity needs to move toward “development without destruction” that “would allow prosperity without undermining current ecosystem services.” This approach requires recognizing the value of services afforded by ecosystems on multiple scales, from local to regional to global.

The authors also call for policymakers to recognize and grant forest-dwelling communities rights over their land, noting research showing showing that legally recognized indigenous territories have significantly lower rates of forest loss in areas of high deforestation pressure.

Finally the authors recommend better management practices — including improved land use planning, less damaging forms of resource extraction and fire control — as well as actions that restore and conserve natural forests, including establishment and maintenance of habitat corridors and protected areas.

“This would lessen the unwelcome shocks that living in the Anthropocene will bring this century,” the authors conclude.

CITATION: Simon L. Lewis, David P. Edwards, David Galbraith. Increasing human dominance of tropical forests. Science 21 August 2015: Vol. 349 no. 6250 pp. 827-832. DOI: 10.1126/science.aaa9932