Differential responses of amphibians and reptiles to land-use change in the biodiversity hotspot of north-eastern Madagascar

Abstract

Large expanses of tropical rainforest have been converted into agricultural landscapes cultivated by smallholder farmers. This is also the case in north-eastern Madagascar; a region that retains a significant proportions of forest cover despite shifting hill rice cultivation and vanilla agroforestry. The region is also a global hotspot for herpetofauna diversity, but how this diversity is affected by land-use change remains largely unknown. Using a space-for-time study design to uncover land-use effects, we compared species diversity and community composition in seven prevalent land uses: unburned (old-growth forest, forest fragment, and forest-derived vanilla agroforest) and burned (fallow-derived vanilla agroforest, woody fallow, herbaceous fallow) land-use types, and rice paddy. We conducted six comprehensives, time-standardized searches across at least ten replicates of each land-use type and applied genetic barcoding to confirm species identification. We documented an outstanding diversity of endemic herpetofauna (119 species): amphibian species richness at the plot level was highest in old-growth forest and significantly lower in all other land-use types. Plot-level reptile species richness was significantly higher in the unburned land-use types than burned land-use types. For both amphibians and reptiles, the less-disturbed land-use types showed more uneven communities and particularly in old-growth forest, the species composition differed significantly from all other land-use types. Amphibians showed a higher level of forest dependency compared to reptiles (38% versus 28% of species exclusively occurred in old-growth forest). Our analyses thus revealed that the two groups respond differently to land-use change: we found less pronounced losses of reptile species richness especially in unburned agricultural habitats, suggesting that reptiles are less susceptible to land-use change than amphibians. Overall, old-growth forest harboured a unique diversity, but some species also thrived in agroforestry systems, especially if these were forest-derived. This highlights the importance of conserving old-growth forests and non-burned land-use types within the agricultural landscape.

Win-win opportunities combining high yields with high multi-taxa biodiversity in tropical agroforestry

“…We sampled amphibians and reptiles using repeated time-standardized search walks for 45 min by two observers 91 . We visited each plot both during the day and at night both during the driest (one nocturnal and one diurnal search between October and December 2017; one nocturnal and one diurnal search between August and December 2018) and the wettest period (one nocturnal and one diurnal search between January and April 2018 or in February 2019).…”

Using land‐use history and multiple baselines to determine bird responses to cocoa agroforestry

“…To partly address this problem, working with multiple controls can be useful. For example, by comparing vanilla agroforests in Madagascar with little-used old-growth forest and heavily used forest fragments, Fulgence et al (2021) found that amphibian communities in agroforests are significantly less species rich than those in old-growth forests but comparable to forest fragments; highlighting both opportunities and limitations of amphibian conservation in agroforestry systems.…”