Assessing Conservation Values: Biodiversity and Endemicity in Tropical Land Use Systems

Abstract

Despite an increasing amount of data on the effects of tropical land use on continental forest fauna and flora, it is debatable whether the choice of the indicator variables allows for a proper evaluation of the role of modified habitats in mitigating the global biodiversity crisis. While many single-taxon studies have highlighted that species with narrow geographic ranges especially suffer from habitat modification, there is no multi-taxa study available which consistently focuses on geographic range composition of the studied indicator groups. We compiled geographic range data for 180 bird, 119 butterfly, 204 tree and 219 understorey plant species sampled along a gradient of habitat modification ranging from near-primary forest through young secondary forest and agroforestry systems to annual crops in the southwestern lowlands of Cameroon. We found very similar patterns of declining species richness with increasing habitat modification between taxon-specific groups of similar geographic range categories. At the 8 km2 spatial level, estimated richness of endemic species declined in all groups by 21% (birds) to 91% (trees) from forests to annual crops, while estimated richness of widespread species increased by +101% (trees) to +275% (understorey plants), or remained stable (- 2%, butterflies). Even traditional agroforestry systems lost estimated endemic species richness by - 18% (birds) to - 90% (understorey plants). Endemic species richness of one taxon explained between 37% and 57% of others (positive correlations) and taxon-specific richness in widespread species explained up to 76% of variation in richness of endemic species (negative correlations). The key implication of this study is that the range size aspect is fundamental in assessments of conservation value via species inventory data from modified habitats. The study also suggests that even ecologically friendly agricultural matrices may be of much lower value for tropical conservation than indicated by mere biodiversity value.

Forest continuity and conservation value in Western Europe

“…The concepts of primary and secondary forest are widely used to guide conservation policy, particularly in tropical regions, where there are often marked differences in structure and composition between primary and secondary forest (Waltert, Bobo et al 2011). Criteria for distinguishing primary from secondary forest in tropical areas are rarely discussed as recent clearance episodes are often easily identified in the field.…”

Supporting conservation with biodiversity research in sub-Saharan Africa’s human-modified landscapes

“…As others have pointed out, understanding the value of human-modified landscapes for biodiversity, especially in Africa, is hampered by data constraints (Norris et al 2010;Pettorelli et al 2010;Waltert et al 2011;Trimble and van Aarde 2012). Many studies are limited in temporal and spatial scale, and poor study design may result in insufficient sampling of habitats.…”

“…The focus on species richness of certain habitat types while failing to account for the importance of species from other habitats in assigning conservation value to different land-use options may neglect the bigger picture; Bond and Parr (2010), for example, call for more collaboration between forest conservationists and others. More consideration for the value of different species in terms of commonness and rarity also needs to be developed because human-modified landscapes often fail to cater for endemic and specialist species (Waltert et al 2011), and a better understanding of beta and gamma diversity at a landscape scale is necessary.…”

The effects of land-use change on the endemic avifauna of Makira, Solomon Islands: endemics avoid monoculture

“…Despite rapid rates of land conversion, few 98 studies have directly looked at the impacts of these changes on patterns of diversity. We examined 99 bird species richness and community assemblage, with a particular focus on endemism and 100 functional traits, to provide further insight into the 'conservation value' (Waltert et al 2011) of the 101 five dominant habitats present within our study area on Makira. Specifically we aimed to quantify 102 the impacts of land-use change on the Makira avifauna by assessing variation, along a gradient of 103 land use intensity, in: 1) species richness, 2) community assemblage, including endemism and 104 functional traits (microhabitat and feeding guild), and 3) species-specific changes in abundance 105 (community structure).…”