Xingli Giam

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

In 2004, Navjot Sodhi and colleagues warned that logging and agricultural conversion of Southeast Asias 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.

The high costs of conserving Southeast Asia's lowland rainforests

Mechanisms that mitigate greenhouse-gas emissions via forest conservation have been portrayed as a cost-effective approach that can also protect biodiversity and vital ecosystem services. However, the costs of conservation – including opportunity costs – are spatially heterogeneous across the globe. The lowland rainforests of Southeast Asia represent a unique nexus of large carbon stores, imperiled biodiversity, large stores of timber, and high potential for conversion to oil-palm plantations, making this region one where understanding the costs of conservation is critical. Previous studies have underestimated the gap between conservation costs and conversion benefits in Southeast Asia. Using detailed logging records, cost data, and species-specific timber auction prices from Borneo, we show that the profitability of logging, in combination with potential profits from subsequent conversion to palm-oil production, greatly exceeds foreseeable revenues from a global carbon market and other ecosystem-service ...

Evaluating the Relative Environmental Impact of Countries

Environmental protection is critical to maintain ecosystem services essential for human well-being. It is important to be able to rank countries by their environmental impact so that poor performers as well as policy ‘models’ can be identified. We provide novel metrics of country-specific environmental impact ranks – one proportional to total resource availability per country and an absolute (total) measure of impact – that explicitly avoid incorporating confounding human health or economic indicators. Our rankings are based on natural forest loss, habitat conversion, marine captures, fertilizer use, water pollution, carbon emissions and species threat, although many other variables were excluded due to a lack of country-specific data. Of 228 countries considered, 179 (proportional) and 171 (absolute) had sufficient data for correlations. The proportional index ranked Singapore, Korea, Qatar, Kuwait, Japan, Thailand, Bahrain, Malaysia, Philippines and Netherlands as having the highest proportional environmental impact, whereas Brazil, USA, China, Indonesia, Japan, Mexico, India, Russia, Australia and Peru had the highest absolute impact (i.e., total resource use, emissions and species threatened). Proportional and absolute environmental impact ranks were correlated, with mainly Asian countries having both high proportional and absolute impact. Despite weak concordance among the drivers of environmental impact, countries often perform poorly for different reasons. We found no evidence to support the environmental Kuznets curve hypothesis of a non-linear relationship between impact and per capita wealth, although there was a weak reduction in environmental impact as per capita wealth increases. Using structural equation models to account for cross-correlation, we found that increasing wealth was the most important driver of environmental impact. Our results show that the global community not only has to encourage better environmental performance in less-developed countries, especially those in Asia, there is also a requirement to focus on the development of environmentally friendly practices in wealthier countries.

Reservoirs of richness: least disturbed tropical forests are centres of undescribed species diversity

In the last few decades, there has been a remarkable discovery of new species of plants, invertebrates and vertebrates, in what have been called the new age of discovery. However, owing to anthropogenic impacts such as habitat conversion, many of the still unknown species may go extinct before being scientifically documented (i.e. ‘crypto-extinctions’). Here, by applying a mathematical model of species descriptions which accounts for taxonomic effort, we show that even after 250 years of taxonomic classification, about 3050 amphibians and at least 160 land mammal species remain to be discovered and described. These values represent, respectively, 33 and 3 per cent of the current species total for amphibians and land mammals. We found that tropical moist forests of the Neotropics, Afrotropics and Indomalaya probably harbour the greatest numbers of undescribed species. Tropical forests with minimal anthropogenic disturbance are predicted to have larger proportions of undescribed species. However, the protected area coverage is low in many of these key biomes. Moreover, undescribed species are likely to be at a greater risk of extinction compared with known species because of small geographical ranges among other factors. By highlighting the key areas of undescribed species diversity, our study provides a starting template to rapidly document these species and protect them through better habitat management.

The world's rediscovered species: Back from the brink?

Each year, numerous species thought to have disappeared are rediscovered. Yet, do these rediscoveries represent the return of viable populations or the delayed extinction of doomed species? We document the number, distribution and conservation status of rediscovered amphibian, bird, and mammal species globally. Over the past 122 years, at least 351 species have been rediscovered, most occurring in the tropics. These species, on average, were missing for 61 years before being rediscovered (range of 3–331 years). The number of rediscoveries per year increased over time and the majority of these rediscoveries represent first documentations since their original description. Most rediscovered species have restricted ranges and small populations, and 92% of amphibians, 86% of birds, and 86% of mammals are highly threatened, independent of how long they were missing or when they were rediscovered. Under the current trends of widespread habitat loss, particularly in the tropics, most rediscovered species remain on the brink of extinction.

Mitigating the impact of oil‐palm monoculture on freshwater fishes in Southeast Asia

Anthropogenic land-cover change is driving biodiversity loss worldwide. At the epicenter of this crisis lies Southeast Asia, where biodiversity-rich forests are being converted to oil-palm monocultures. As demand for palm oil increases, there is an urgent need to find strategies that maintain biodiversity in plantations. Previous studies found that retaining forest patches within plantations benefited some terrestrial taxa but not others. However, no study has focused on aquatic taxa such as fishes, despite their importance to human well-being. We assessed the efficacy of forested riparian reserves in conserving freshwater fish biodiversity in oil-palm monoculture by sampling stream fish communities in an oil-palm plantation in Central Kalimantan, Indonesia. Forested riparian reserves maintained preconversion local fish species richness and functional diversity. In contrast, local and total species richness, biomass, and functional diversity declined markedly in streams without riparian reserves. Mechanistically, riparian reserves appeared to increase local species richness by increasing leaf litter cover and maintaining coarse substrate. The loss of fishes specializing in leaf litter and coarse substrate decreased functional diversity and altered community composition in oil-palm plantation streams that lacked riparian reserves. Thus, a land-sharing strategy that incorporates the retention of forested riparian reserves may maintain the ecological integrity of fish communities in oil-palm plantations. We urge policy makers and growers to make retention of riparian reserves in oil-palm plantations standard practice, and we encourage palm-oil purchasers to source only palm oil from plantations that employ this practice.

The extent of undiscovered species in Southeast Asia

Southeast Asia has the highest rate of deforestation among all tropical regions in the world. Depending on the number of undiscovered species not yet known to science, a sizeable proportion of species may have gone extinct or will go extinct in the future without record. We compiled species datasets for eight taxa, each consisting of a list of native species and their description dates. Birds, legumes, mosquitoes, and mosses showed recent declines in species discovery rate. For these taxa, we estimated the total species richness by applying generalized linear models derived from theory. The number of undiscovered species in each taxon was calculated and the extent of undiscovered species among the taxa compared. Among these taxa that displayed a species discovery decline, the legumes had the highest extent of undiscovered species while the birds had the most complete species inventory. Although quantitative estimates of the number of undiscovered species for amphibians, freshwater fish, hawkmoths, and mammals could not be derived, the extent of undiscovered species is likely to be high as their recent discovery rates showed a continued increase. If these taxa are more or less representative of other Southeast Asian taxa, many species are likely to go extinct before ever being discovered by science under the current rates of habitat loss. We therefore urge the intensification of taxonomic and species discovery research in the taxa in which the extent of undiscovered species is relatively high, i.e., amphibians, freshwater fish, hawkmoths, mammals, and legumes.

Global extinctions of freshwater fishes follow peatland conversion in Sundaland

The peat swamp forests (PSFs) of Sundaland, in Southeast Asia, support many endemic freshwater fish species. However, the future of these species is in doubt, owing to ongoing PSF deforestation. Here, we show that, if current rates of PSF conversion to a predominantly agricultural mosaic landscape continue through 2050, 16 fish species may become globally extinct. In the worst-case scenario, where the rate of conversion across the region matches that of the most rapidly deforested river basin, 77% (79 of 102 species) of the narrowly adapted (stenotopic) fish species are likely to become extinct, a figure that would more than double known extinctions of the worlds freshwater fishes. As indicated by our analysis, the PSFs of Indonesias Central Kalimantan region would be most severely impacted.

Estimating How Many Undescribed Species Have Gone Extinct

Because both descriptions of species and modern human-driven extinctions started around the same time (i.e., eighteenth century), a logical expectation is that a large proportion of species may have gone extinct without ever having been recorded. Despite this evident and widely recognized assumption, the loss of undescribed species has never been estimated. We quantified this loss for several taxonomic groups and regions for which undescribed species extinctions are likely to have occurred. Across a wide range of taxonomic groups, we applied known extinction rates computed from recorded species losses to assumed exponential decay in the proportion of species remaining undiscovered. Because all previous modeling attempts to project total species richness implicitly assumed that undescribed species extinctions could be neglected, we also evaluated the effect of neglecting them. Finally, because we assumed constant description and extinction probabilities, we applied our model to simulated data that did not conform to this assumption. Actual species losses were severely underestimated by considering only known species extinctions. According to our estimates, the proportion of undiscovered extinct species over all extinctions ranged from 0.15 to 0.59, depending on the taxonomic group and the region considered. This means that recent extinctions may be up to twice as large as the number recorded. When species differed in their extinction or description probabilities, our model underestimated extinctions of undescribed species by up to 20%.

The ecology and economics of shorebird conservation in a tropical human‐modified landscape

Summary Rapid and extensive land-use change in intertidal foraging habitat and coastal roosting habitat is thought to be driving major population declines of shorebirds migrating through the East Asian–Australasian Flyway. Along the Inner Gulf of Thailand, a critical stopover and wintering ground for these birds, artificial wetlands (salt pans and aquaculture ponds) have replaced much of the natural coastal ecosystem. We conducted a two-part study to (i) assess the importance of salt pans and semi-traditional aquaculture ponds to shorebirds and (ii) understand the economic forces that drive land-use change in this region by interviewing salt pan and aquaculture operators. Salt pans provide important roost habitat, particularly for shorter-legged birds, which are less able to utilize aquaculture ponds due to their greater depth. Moreover, three focal shorebird species foraged extensively in salt pans and semi-traditional aquaculture ponds, even when intertidal mudflats were exposed, suggesting that artificial wetlands could buffer against the impacts of degraded intertidal foraging areas for some shorebird species. Economic profits from salt production and semi-traditional aquaculture are similar. Risks to investment and per capita profitability are key factors in determining whether to convert land from one use (e.g. salt pan) to the other (aquaculture). Synthesis and applications. Salt pans provide an important resource to migrating shorebirds. As development pressures increase, operators may need financial incentives if salt pans are to be maintained over large areas. Although semi-traditional aquaculture is used less by shorebirds, drained ponds provide opportunities to roost and forage. Semi-traditional aquaculture operators should drain their ponds regularly to provide supplementary habitat for shorebirds. Use of nets and pond liners should be discouraged in both systems. Optimizing aquaculture pond and salt pan management for shorebirds could provide a more pragmatic, cost-effective and geographically extensive solution to conserving these birds than protected areas alone.