Diversity of mammals in a biodiversity enriched oil palm plantation

Motivation

Land-use conversion to cash tree plantations has rendered the multidiverse Southeast Asian continent a hotspot of the global biodiversity crisis. The wave of extinction does not hold at iconic mammals such as tigers, clouded leopards, tapirs and gibbons plus 80+ more species. The effects become apparent in the loss of ecosystem functioning. It is the species’ environmental interaction which substantiates community composition, distribution of biomass and the structure of ecosystems. While herbivores and omnivores directly shape autotroph diversity as consumers and seed dispersers (Derhé et al., 2018), trophic cascades, often mediated by carnivores, act as balancing force, ensuring beneficial effects on ecosystem resilience (Hoeks et al., 2020).
The recovery of mammal diversity in biodiversity enriched oil palm plantations is yet to be assessed. Ten years have passed since the establishment of the EFForTS project of which my research will be part. This provides a reasonable time horizon for the investigation of the impacts of tree islands on mammal diversity.

Objectives and Methods

I will characterize the small to medium sized mammal diversity using camera traps which will be installed in a way that guarantees the full coverage of plot sizes and diversity levels. This will allow me to differentiate among the conservation effectivity of these design elements of tree islands as well as the effect of other important variables including the proximity to natural forest, the ground and overstorey vegetation cover and tree species composition. Knowing the habitat preferences of mammals in relation to their population status will enable the optimization of agroforestry systems towards conservation of endangered species.
Species richness and occupancy modelling-derived abundance estimates (Royle Biometrics) will serve as a basis for well-known diversity indices (Shannon, Simpson) and regression analysis to the named cofactors.

Hypothesis

Based on previous research I expect that the mammalian species richness will be elevated as compared to usual monocultures but still substantially compromised as compared to primary forests. Based on the findings of Maddox et al. (2007) the integration of tree islands might increase the tolerance level of each species, meaning that species with moderate tolerance might be spotted more frequently whereas species that showed a complete avoidance of oil palm might be occasionally captured passing through the forest or using it as a resource.

This master thesis is supervised by Gustavo Paterno and Jeremy Larroque.