Review
Navjot's nightmare revisited: logging, agriculture, and biodiversity in Southeast Asia

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Highlights

  • Southeast Asia has the highest rates of forest degradation and conversion in the tropics.

  • New research shows that forest conversion to cropland, especially oil palm, results in much greater losses of biodiversity than does even intensive logging.

  • There is little evidence that crops such as oil palm or rubber can be grown in ways that sustain forest-dependent species.

  • Preventing the conversion of logged forest to cropland should be a top priority of conservationists; moreover, it provides a cost-effective way to protect much (but not all) of the forest biodiversity of the region.

In 2004, Navjot Sodhi and colleagues warned that logging and agricultural conversion of Southeast Asia's forests were leading to a biodiversity disaster. We evaluate this prediction against subsequent research and conclude that most of the fauna of the region can persist in logged forests. Conversely, conversion of primary or logged forests to plantation crops, such as oil palm, causes tremendous biodiversity loss. This loss is exacerbated by increased fire frequency. Therefore, we conclude that preventing agricultural conversion of logged forests is essential to conserving the biodiversity of this region. Our analysis also suggests that, because Southeast Asian forests are tightly tied to global commodity markets, conservation payments commensurate with combined returns from logging and subsequent agricultural production may be required to secure long-term forest protection.

Section snippets

Revisiting Navjot's nightmare

In an influential paper published in TREE in 2004, Navjot Sodhi and colleagues described an impending biodiversity disaster in Southeast Asia [1]. The disaster, they argued, stemmed from several factors, including deforestation, overexploitation of wildlife, commercial logging, and anthropogenic fire, all of which were happening in a region of high species richness and endemism. Sodhi and colleagues flagged deforestation and logging as the most urgent threats, noting that Southeast Asia had the

Deforestation in Southeast Asia

Deforestation remains a serious problem in Southeast Asia. The Forest Resources Assessment 2010 of the Food and Agriculture Organization revealed that primary forest (see Glossary) in the ten Southeast Asian countries decreased from approximately 663 000 km2 in 2000 to approximately 640 000 km2 in 2010 (–0.35% year–1; Table S1 in the supplementary material online) [4]. The decline of secondary and selectively logged forests (i.e., ‘naturally regenerating forests’ sensu the FAO) was even more

Impacts of forest conversion on biodiversity

Several studies, both recent and older, have examined how various taxa are affected by different types of forest conversion. Approximately 75% of forest-dwelling bird species 12, 13 and approximately 80% of forest-dwelling butterflies 6, 14, 15 are lost when forests are converted to oil palm plantations. There is also a dramatic shift in the community composition of bees [16]. Furthermore, most International Union for the Conservation of Nature (IUCN) Red-listed bird species do not persist

Impacts of logging on biodiversity

Throughout Southeast Asia, forests that are not being converted to food crops, oil palm, or pulp-and-paper plantations are being logged to various degrees. Even parks and preserves that are nominally off limits to loggers are nonetheless susceptible to illegal logging [27]. Fortunately, we now have a better understanding of the impacts of large-scale commercial logging, as well as RIL (Box 2), on biodiversity than was the case in 2004. A first round of selective logging, for example, the

Economic insights

The economic drivers and consequences of land-use change in Southeast Asia are complex. There are certainly private and social costs and benefits associated with any land-use decision; however, the weight of evidence suggests that the conversion of forests in Southeast Asia is tightly tied to global commodity markets [42] and has been since at least the tropical timber boom of the 1980s [43]. The pressure of global commodity demand does not seem to be easing off, with the real prices (a proxy

Conservation recommendations

Taken together, the body of recent research in Southeast Asia points to three important conclusions about the forests of the region. First, in terms of protecting the full array of vulnerable plants and animals, there is no substitute for conserving the remaining primary forests 39, 57.

Second, the profitability of logging and oil palm agriculture makes protection of those unlogged forests exceedingly expensive, except in places where topographic conditions, distance to markets, and other

Concluding remarks

Nearly a decade after Sodhi et al.’s call to arms [1], we have a much deeper understanding of the myriad ecological and economic issues underlying the ongoing biodiversity crisis in Southeast Asia. It is a crisis driven largely by the conversion of forests to croplands, especially oil palm and rubber. (Selective logging poses a lesser threat, largely because most, but not all, of the species found in primary forests appear to be able to persist in logged forests.) In addition, it is a crisis

Acknowledgments

We thank Bert Harris, Tien Ming Lee, and three anonymous reviewers for their helpful comments on this manuscript. We also thank Jukka Miettinen for advice and discussions on fires in Southeast Asia. Our work in Southeast Asia has been supported in part by a grant from the High Meadows Foundation to D.S.W.

Glossary

Deforestation
an activity whereby intact forest is clearcut and not allowed or able to regenerate as forest, or is replaced with a nonforest landcover, such as agriculture.
Forest conversion
an activity whereby native forest is cleared and replaced with a nonforest landcover (e.g., agriculture including oil palm and rubber, timber plantations, urban land, open land, etc.).
Intact forest
(as defined in Box 1 and Figure 1) this landcover class includes primary forest, mature secondary forest, and

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