The oil palm conundrum: How oil palm agriculture affects tropical biodiversity and what can we do about it.

摘要

The oil palm (Elaeis guineensis) is one of the most rapidly expanding equatorial crops in the world. In the major oil palm-producing countries (e.g., Indonesia and Malaysia), oil palm agriculture poses a significant threat to tropical forests and biodiversity. On the other hand, the oil palm industry contributes substantially to the economies of these developing nations, and is important to the livelihoods of many rural communities. To determine how oil palm agriculture affects tropical forests and biodiversity, and explore ways by which we could reconcile human livelihood and biodiversity conservation in oil palm-producing countries, I address the following questions: (1) Will oil palm agriculture continue to pose a significant threat to Southeast Asia's biodiversity in the future? (2) What types of land were oil palm plantations converted from? And what is the biodiversity value of oil palm plantations relative to these prior land-uses? (3) What are the biodiversity impacts of different oil palm management systems? How and to what extent can oil palm plantations be made more hospitable for biodiversity? (4) Does biodiversity in an oil palm plantation provide any ecosystem service for oil palm agriculture? (5) What approaches are needed to conserve Southeast Asia's biodiversity in the face of intense land-use competition from oil palm agriculture? In chapter 1, I show that rising global demand for biodiesel could result in substantial agricultural expansion in all of the current major feedstocks, including oil palm, and could cause significant losses of natural habitats (rapeseed: 25.9-34.9 million ha; sunflower seed: 56.0-61.1 million ha; soybean: 76.4-114.2 million ha; oil palm: 0.4-5.4 million ha). In chapter 2, I show that during the period 1990-2005, between 55% and 59% of the total extent of oil palm expansion in Malaysia, and at least 56% of that in Indonesia likely had occurred at the expense of forests. I also show that the conversion of either old-growth forests or secondary (logged) forests to oil palm plantations results in significant biodiversity losses, while the conversion of cropland (rubber) to oil palm plantations is markedly less damaging. In chapter 3, I show that the species richness of forest butterflies and birds in oil palm plantations could be marginally enhanced by adopting biodiversity-friendly management practices at the local scale (e.g., retaining epiphytes on palm trees), and by increasing the amount of natural forest cover at the landscape scale. In chapter 4, I present results from a bird exclusion experiment, which show that bird exclusion significantly increased herbivory rates compared to control treatments, and that the effect size of bird exclusion (i.e., magnitude of insect control) increased with the abundance of insectivorous birds. In chapter 5, I propose a novel strategy for conserving biodiversity in oil palm-producing countries, which is for conservation groups, oil palm companies and local governments to work together to use some of the profits from oil palm agriculture to fund conservation efforts. I present a worked example of how a hypothetical 5,000 ha oil palm plantation could generate annual profits amounting to some US{dollar}10 million, which could be used to acquire ∼36,000 ha of forests over 20 years.