Dadang Dwi Putra

Combining high biodiversity with high yields in tropical agroforests

Local and landscape-scale agricultural intensification is a major driver of global biodiversity loss. Controversially discussed solutions include wildlife-friendly farming or combining high-intensity farming with land-sparing for nature. Here, we integrate biodiversity and crop productivity data for smallholder cacao in Indonesia to exemplify for tropical agroforests that there is little relationship between yield and biodiversity under current management, opening substantial opportunities for wildlife-friendly management. Species richness of trees, fungi, invertebrates, and vertebrates did not decrease with yield. Moderate shade, adequate labor, and input level can be combined with a complex habitat structure to provide high biodiversity as well as high yields. Although livelihood impacts are held up as a major obstacle for wildlife-friendly farming in the tropics, our results suggest that in some situations, agroforests can be designed to optimize both biodiversity and crop production benefits without adding pressure to convert natural habitat to farmland.

Alpha and beta diversity of plants and animals along a tropical land-use gradient

Assessing the overall biological diversity of tropical rain forests is a seemingly insurmountable task for ecologists. Therefore, researchers frequently sample selected taxa that they believe reflect general biodiversity patterns. Usually, these studies focus on the congruence of alpha diversity (the number of species found per sampling unit) between taxa rather than on beta diversity (turnover of species assemblages between sampling units). Such approaches ignore the potential role of habitat heterogeneity that, depending on the taxonomic group considered, can greatly enhance beta diversity at local and landscape scales. We compared alpha and beta diversity of four plant groups (trees, lianas, terrestrial herbs, epiphytic liverworts) and eight animal groups (birds, butterflies, lower canopy ants, lower canopy beetles, dung beetles, bees, wasps, and the parasitoids of the latter two) at 15 sites in Sulawesi, Indonesia, that represented natural rain forest and three types of cacao agroforests differing in management intensity. In total, we recorded 863 species. Patterns of species richness per study site varied strongly between taxonomic groups. Only 13-17% of the variance in species richness of one taxonomic group could be predicted from the species richness of another, and on average 12-18% of the variance of beta diversity of a given group was predicted by that in other groups, although some taxon pairs had higher values (up to 76% for wasps and their parasitoids). The degree of congruence of patterns of alpha diversity was not influenced by sampling completeness, whereas the indicator value for beta diversity improved when using a similarity index that accounts for incomplete sampling. The indication potential of alpha diversity for beta diversity and vice versa was limited within taxa (7-20%) and virtually nil between them (0-4%). We conclude that different taxa can have largely independent patterns of alpha diversity and that patterns of beta diversity can be more congruent. Thus, conservation plans on a landscape scale need to put more emphasis on the high heterogeneity of agroforests and the overarching role of beta diversity shaping overall diversity patterns.

The value of differently managed cacao plantations for forest bird conservation in Sulawesi, Indonesia

In order to assess the potential value of differently managed cacao plantations for bird conservation on Sulawesi, we surveyed birds in near-primary forest (with limited timber and rattan extraction, and some hunting), cacao plantations with remnant forest trees and plantations lacking forest trees, from February to April 2007. A total of 16 50 x 50 m plots were visited twice and records of 87 species were obtained. Bird species richness and the number of endemics and forest specialists decreased along this gradient of forest conversion, with 20% of the forest specialists, among them 10 endemics, exclusively found in forest. Species composition changed dramatically between habitat types. Sorensen indices showed a similarity of species composition between forests and plantations of 45–60% for forest specialists and 65–71% for all species. The most important environmental variable for the diversity and composition of birds was the number of remnant rainforest trees present in the plantations. Our results suggest that large, undisturbed rainforest are most important for the conservation of forest specialists and endemics but that cacao plantations, if managed to maintain a high and diverse cover of forest trees, can harbour up to 60% of forest specialists and endemics.

Biodiversity patterns and trophic interactions in human-dominated tropical landscapes in Sulawesi (Indonesia): plants, arthropods and vertebrates

The need to capture primary production in order to sustain and improve economic livelihoods has lead to increasing conversion of natural habitat and intensification of agricultural practices in many parts of the world including most tropical regions. Understanding how these processes affect ecosystems and their functioning, in particular in the high-diversity ecosystems of the tropics, has become a key issue in ecological research. In this chapter, our focus is on the agriculture-forest landscapes of Central Sulawesi, Indonesia, an island widely known for its endemic yet still poorly known flora and fauna. The rise of the region to one of the largest cacao producing areas in the world is at the core of recent land-use change and intensification processes. Covering plants (trees, rattan palms, herbs, bryophytes) and several invertebrate (ants, dung beetles, cacao insect herbivores, fruit-feeding butterflies, parasitic Hymenoptera, spiders) and vertebrate groups (amphibians, birds, murids, reptiles), we give an in-depth overview of the determinants of biodiversity in cacao landscapes, including both management and landscape-scale variables into our analyses. Results show that shaded agroforests host a rich community of species. By adopting a large-scale study design we showed that proximity of natural forest is a key predictor for species richness of plants, invertebrates and vertebrates alike. Endemics and forest specialists benefit most from indigenous shade tree cover and proximity to natural forest. Importantly, several functionally important groups such as insectivorous and seed-dispersing birds benefit from tall shade trees, shade tree diversity and proximity to forest edge, while parasitoid diversity is greatest close to natural forests. Available data on the effects of landuse change in cacao landscape of Central Sulawesi is increasing. Change in landscape configuration and management practices are being clearly reflected in the composition of species communities, with likely impacts on ecosystem services such as pest control and pollination. More knowledge is needed especially in terms of species interactions and ecosystem functioning, but also on how existing knowledge can contribute to effective conservation in human-dominated landscapes outside protected areas.