9,345 research outputs found
Amphibian and butterfly diversity across a tropical land-use gradient in Sri Lanka: implications for conservation decision making
No full textE.P. Kudavidanage, T.C. Wanger, C. de Alwis, S. Sanjeewa and S.W. Kotagam
Land use changes imperil South-East Asian biodiversity
No full textNavjot S. Sodhi, Mary Rose C. Posa, Kelvin S.-H. Peh, Lian Pin Koh, Malcolm C.K. Soh, Tien Ming Lee, Janice S.H. Lee, Thomas C. Wanger and Barry W. Broo
Conserving imperiled species: a comparison of the IUCN Red List and U.S. Endangered Species Act
No full textAbstract
The United States conserves imperiled species with the Endangered Species Act (ESA). No studies have evaluated the ESA's coverage of species on the International Union for Conservation of Nature (IUCN) Red List, which is an accepted standard for imperiled species classification. We assessed the ESA's coverage of IUCN‐listed birds, mammals, amphibians, gastropods, crustaceans, and insects, and studied the listing histories of three bird species and Pacific salmonids in more detail. We found that 40.3% of IUCN‐listed U.S. birds are not listed by the ESA, and most other groups are underrecognized by >80%. Species with higher IUCN threat levels are more frequently recognized by the ESA. Our avian case studies highlight differences in the objectives, constraints, and listing protocols of the two institutions, and the salmonids example shows an alternative situation where agencies were effective in evaluating and listing multiple (related) species. Vague definitions of
endangered
and
threatened
, an inadequate ESA budget, and the existence of the
warranted but precluded
category likely contribute to the classification gap we observed.
J. Berton C. Harris, J. Leighton Reid, Brett R. Scheffers, Thomas C. Wanger, Navjot S. Sodhi, Damien A. Fordham & Barry W. Broo
Endemic predators, invasive prey and native diversity
No full textInteractions between native diversity and invasive species can be more complex than is currently understood. Invasive ant species often substantially reduce diversity in the native ants diversity that act as natural control agents for pest insects. In Indonesia (on the island of Sulawesi), the third largest cacao producer worldwide, we show that a predatory endemic toad (Ingerophrynus celebensis) controls invasive ant (Anoplolepis gracilipes) abundance, and positively affects native ant diversity. We call this the invasive-naivety effect (an opposite of enemy release), whereby alien species may not harbour anti-predatory defences against a novel native predator. A positive effect of the toads on native ants may facilitate their predation on insect vectors of cacao diseases. Hence, toads may increase crop yield, but further research is needed on this aspect. Ironically, amphibians are globally the most threatened vertebrate class and are strongly impacted by the conversion of rainforest to cacao plantations in Sulawesi. It is, therefore, crucial to manage cacao plantations to maintain these endemic toads, as they may provide critical ecosystem services, such as invasion resistance and preservation of native insect diversity.Thomas C. Wanger, Arno C. Wielgoss, Iris Motzke, Yann Clough, Barry W. Brook, Navjot S. Sodhi and Teja Tscharntk
Conserving Southeast Asian forest biodiversity in human-modified landscapes
No full textSoutheast Asia experiences one of the highest rates of deforestation in the tropics due to agricultural expansion, logging, habitat fragmentation and urbanization, which are expected to result in species declines and extinctions. In particular, growing global demands for food, biofuel and other commodities are driving the rapid expansion of oil palm and paper-and-pulp industries at the expense of lowland dipterocarp forests, further jeopardizing Southeast Asian forest biotas. We synthesize recent findings on the effects of land-use changes on plants, invertebrates, vertebrates and ecosystem functioning/services in Southeast Asia. We find that species richness and abundance/density of forest-dependent taxa generally declined in disturbed compared to mature forests. Species with restricted ranges and those with habitat and foraging specialization were particularly vulnerable. Forest loss also disrupted vital ecosystem services (e.g. crop pollination). Long-term studies are needed to understand biotic sustainability in regenerating and degraded forests, particularly in the context of the synergistic or additive effects of multiple agents of biodiversity loss (e.g. invasive species and climate change). The preservation of large tracts of mature forests should remain the principal conservation strategy in the tropics. In addition, reforestation and reintroductions of native species, as well as improved connectivity among forest patches could enhance the conservation value of forest remnants in human-dominated landscapes. © 2009 Elsevier Ltd.Navjot S. Sodhi, Lian Pin Koh, Reuben Clements, Thomas C. Wanger, Jane K. Hill, Keith C. Hamer, Yann Clough, Teja Tscharntke, Mary Rose C. Posa and Tien Ming Leehttp://www.elsevier.com/wps/find/journaldescription.cws_home/405853/description#descriptio
Effects of land-use change on community composition of tropical amphibians and reptiles in Sulawesi, Indonesia
No full textLittle is known about the effects of anthropogenic land-use change on the amphibians and reptiles of the biodiverse tropical forests of Southeast Asia. We studied a land-use modification gradient stretching from primary forest, secondary forest, natural-shade cacao agroforest, planted-shade cacao agroforest to open areas in central Sulawesi, Indonesia. We determined species richness, abundance, turnover, and community composition in all habitat types and related these to environmental correlates, such as canopy heterogeneity and thickness of leaf litter. Amphibian species richness decreased systematically along the land-use modification gradient, but reptile richness and abundance peaked in natural-shade cacao agroforests. Species richness and abundance patterns across the disturbance gradient were best explained by canopy cover and leaf-litter thickness in amphibians and by canopy heterogeneity and cover in reptiles. Amphibians were more severely affected by forest disturbance in Sulawesi than reptiles. Heterogeneous canopy cover and thick leaf litter should be maintained in cacao plantations to facilitate the conservation value for both groups. For long-term and sustainable use of plantations, pruned shade trees should be permanently kept to allow rejuvenation of cacao and, thus, to prevent repeated forest encroachment.Thomas C. Wanger, Djoko T. Iskandar, Iris Motzke, Barry W. Brook, Navjot S. Sodhi, Yann Clough, and Teja Tscharntk
Pollination mitigates cucumber yield gaps more than pesticide and fertilizer use in tropical smallholder gardens
No full textPollination can be an essential but often neglected ecosystem service to mitigate crop yield gaps. Pollination services are usually studied in isolation, and their relative role and possible interactions with other factors, such as major management practices, is little understood. We tested how pollination (insect vs. wind- and self-pollination) interacts with weed control, fertilization and insect herbivore control and how these factors as well as flower-visiting bees influence fruit set and yield of cucumber Cucumis sativus L. in 13 traditional Indonesian home gardens. Although insect pollination, fertilization and weed control additively increased crop yield, fertilization and weed control alone could not compensate for pollination loss. Pollination individually accounted for 75% of the yield and was, hence, the most important driver of yield. In contrast, herbivore control through insecticides at commonly applied levels did not increase yield. Yield strongly increased with higher number of flower-visiting bee individuals, while the number of bee individuals in turn was not influenced by weed control, fertilization or herbivore control, but increased with higher number of cucumber flowers. Synthesis and applications. Although multiple management practices influence yield, they cannot compensate yield gaps from pollinator loss in cucumber smallholder production in Indonesia. Our results also show that the widespread use of insecticides without considering the impacts on pest reduction is uneconomical. Here, reducing insecticides caused no income loss and, at the same time, reduces potential risks to important pollinators, which needs to be acknowledged by policy-driven regulations for pesticide application in tropical agroecosystems. Our results stress the importance of enhancing bee populations to facilitate pollination services. Bee management practices, such as sustaining additional food resources for pollinators, need to be established
Cocoa production: Monocultures are not the solution to climate adaptation—Response to Abdulai et al. 2017
No full textCocoa is a major trade commodity that is seeing increasing demand, but also climate-related yield declines1 . There has been an ongoing discussion whether both, the effective adaptation of plantations to climate change and a long term increase of cocoa yields, can only be achieved with shaded agroforestry or also with full-sun monocultures2 . Abdulai et al. 3 investigated the climate adaptation potential of full-sun cocoa monocultures and shaded agroforestry in Ghana West Africa. This article is protected by copyright. All rights reserved
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