Orangutan movement and population dynamics across human-modified landscapes: implications of policy and management

Dave J I Seaman,Justin M J Travis,Erik Meijaard,Greta Bocedi,Serge Wich,Henry Bernard,Marc Ancrenaz,Stephen C F Palmer,Matthew J Struebig,Tatyana Humle,Maria Voigt,Nicolas J Deere

doi:10.1007/s10980-021-01286-8

Abstract

ContextAgricultural expansion is a leading cause of deforestation and habitat fragmentation globally. Policies that support biodiversity and facilitate species movement across farmland are therefore central to sustainability efforts and wildlife conservation in these human-modified landscapes.ObjectivesWe investigated the conservation impact of several potential management scenarios on animal populations and movement in a human-modified tropical landscape, focusing on the critically endangered Bornean orangutan, Pongo pygmaeus.MethodsWe used an individual-based modelling platform to simulate population dynamics and movements across four possible landscape management scenarios for a highly modified oil palm-dominated landscape in Sabah, Malaysian Borneo.ResultsScenarios that maximised the retention of natural forest remnants in agricultural areas through sustainability certification standards supported stable orangutan populations. These populations were up to 45% larger than those supported under development-focused scenarios, where forest retention was not prioritised. The forest remnants served as corridors or stepping-stones, increasing annual emigration rates across the landscape, and reducing orangutan mortality by up to 11%. Sensitivity analyses demonstrated that this outcome was highly contingent on minimising mortality during dispersal.ConclusionsManagement that promotes maximising natural forest cover through certification, such as that promoted by the Roundtable on Sustainable Palm Oil, can maintain viable orangutan populations over the lifespan of an oil palm plantation and facilitate movement among otherwise isolated populations. However, minimising hunting and negative human–orangutan interactions, while promoting peaceful co-existence between apes and people, will be imperative to insure positive conservation outcomes.

Highlights

Agricultural expansion is the leading cause of deforestation and biodiversity loss across the tropics (Curtis et al 2018)
Scenarios that maximised the retention of natural forest remnants in agricultural areas through sustainability certification standards supported stable orangutan populations
Sensitivity analyses demonstrated that this outcome was highly contingent on minimising mortality during dispersal

Summary

Introduction

Agricultural expansion is the leading cause of deforestation and biodiversity loss across the tropics (Curtis et al 2018). The demand for commodities and the need to sustain an increasing human population means further agricultural expansion will be unavoidable (Laurance et al 2014). Biodiversity is heavily impoverished in intensively managed oil palm plantations, which typically support \ 15% of the species found in native forests (Fitzherbert et al 2008; Meijaard et al 2018). There is growing evidence that by retaining forest remnants within plantations and managing them effectively, some wildlife species can survive in these human-modified landscapes (Deere et al 2018, 2019; Mitchell et al 2018). There is an increasing emphasis on including human-modified landscapes into the broader agenda of wildlife conservation in tropical countries (Ng et al 2020)

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