Old-growth rainforests vital for tropical biodiversity: study

Sep 14, 2011
A dawn mist rises above the Amazon rainforest. Credit: William Laurance

A team of researchers from Singapore, Australia, Switzerland, the UK and the USA has carried out a comprehensive assessment to estimate the impact of disturbance and land conversion on biodiversity in tropical forests. In a recent study published in Nature, they found that primary forests – those least disturbed old-growth forests – sustain the highest levels of biodiversity and are vital to many tropical species.

Rampant rates of logging and agricultural expansion have transformed the world's , leaving little remaining primary forests unaltered by humans. The value of these rapidly expanding degraded and converted forest landscapes is hotly debated, and was the subject of the study.

"Some scientists have recently argued that degraded tropical forests support high levels of ," says Luke Gibson, the lead author from the National University of Singapore (NUS). "Our study demonstrates that this is rarely the case," he adds.

Drawing on information from 138 scientific studies spanning 28 tropical countries, Gibson and his colleagues compared biodiversity in primary forests to that in regenerating forests and forests degraded by logging and converted to agriculture. Overall, biodiversity values were substantially lower in disturbed forests.

"There's no substitute for primary forests," says Gibson. "All major forms of disturbance invariably reduce biodiversity in tropical forests," he adds.

Selective logging, in which machinery is used to extract a limited number of trees from the forest, appears to be the least harmful human disturbance. "As selective logging is rapidly expanding throughout the tropics, ecological restoration of such areas might represent an effective strategy to alleviate threats to biodiversity," says Lian Pin Koh of ETH Zurich.

Parks, however, will remain a critical conservation strategy in protecting the world's remaining primary tropical forests. "We urgently need to expand our reserves and improve their enforcement," says Tien Ming Lee, co-lead author at the University of California, San Diego. "Effective reserves have the added benefit of reducing overall carbon emissions", adds Lee.

However, many of these tropical parks are far from secure. "A growing number of reserves are being degraded, downsized, if not entirely degazetted, so holding on to the last remaining large tracts of primary forests within existing reserves will be a crucial part of the conservation mission this century", says Carlos Peres of the University of East Anglia.

Compared to Africa and the Americas, the authors found that tropical forests in Asia suffered the greatest loss in biodiversity. "Southeast Asia, representing most of the Asian studies, emerged as a conservation hotspot and must be one of our top priority regions," suggests Lee. Not surprisingly, Southeast Asia has the lowest remaining forest cover, highest rates of deforestation, and the highest human population densities among all major tropical regions.

This study was initiated by the late Professor Navjot Sodhi, a renowned conservation ecologist at NUS, who devoted his career to studying the biodiversity crisis in Southeast Asia and around the planet.

With the global population projected to surpass 9 billion by 2050, tropical forests will face increasing threats posed by human-driven land-use changes. "Human populations are exploding and very few areas remain untouched by the expanding horizon of human impacts," says Gibson, who was mentored by Professor Sodhi. "It is therefore essential to limit the reach of humans and to preserve the world's remaining old-growth rainforests while they still exist. The future of tropical biodiversity depends on it," he concludes.

Explore further: Monitoring heavy metals using mussels

More information: Primary forests are irreplaceable for sustaining tropical biodiversity, Luke Gibson, Tien Ming Lee, Lian Pin Koh, Barry W. Brook, Toby A. Gardner, Jos Barlow, Carlos A. Peres, Corey J. A. Bradshaw, William F. Laurance, Thomas E. Lovejoy & Navjot S. Sodhi, Nature September 14, 2011. doi:10.1038/nature10425

Provided by National University of Singapore

5 /5 (4 votes)

Related Stories

Global tropical forests threatened by 2100

Aug 05, 2010

By 2100 only 18% to 45% of the plants and animals making up ecosystems in global, humid tropical forests may remain as we know them today, according to a new study led by Greg Asner at the Carnegie Institution's ...

New technology needed to monitor rain forest 'tsunami'

Jan 12, 2009

Human impact on tropical forest ecosystems has reached a "tsunami" stage, say scientists, and will require a new generation of sophisticated remote-sensing technology to monitor the changes. Speaking at a January 12, 2009 ...

Recommended for you

Monitoring heavy metals using mussels

2 hours ago

A research team in Malaysia has concluded that caged mussels are useful for monitoring heavy metal contamination in coastal waters in the Strait of Johore. Initial results indicate more pollution in the eastern ...

Climate change report identifies 'the most vulnerable'

4 hours ago

Extreme weather events leave populations with not enough food both in the short- and the long-term. A new report by the Environmental Change Institute (ECI) at the School of Geography and the Environment ...

Obama readies climate change push at UN summit

7 hours ago

President Barack Obama will seek to galvanize international support in the fight against climate change on Tuesday when he addresses the United Nations, with time running out on his hopes of leaving a lasting ...

New toxic spill traced to Mexico mine

7 hours ago

Civil protection authorities have confirmed new toxic spills in northwestern Mexico, where a massive acid spill from a copper mine contaminated waterways.

User comments : 0