Unexpected Ecological Resilience in Bornean Orangutans and Implications for Pulp and Paper Plantation Management

Abstract

Ecological studies of orangutans have almost exclusively focused on populations living in primary or selectively logged rainforest. The response of orangutans to severe habitat degradation remains therefore poorly understood. Most experts assume that viable populations cannot survive outside undisturbed or slightly disturbed forests. This is a concern because nearly 75% of all orangutans live outside protected areas, where degradation of natural forests is likely to occur, or where these are replaced by planted forests. To improve our understanding of orangutan survival in highly altered forest habitats, we conducted population density surveys in two pulp and paper plantation concessions in East Kalimantan, Indonesia. These plantations consist of areas planted with fast-growing exotics intermixed with stands of highly degraded forests and scrublands. Our rapid surveys indicate unexpectedly high orangutan densities in plantation landscapes dominated by Acacia spp., although it remains unclear whether such landscapes can maintain long-term viable populations. These findings indicate the need to better understand how plantation-dominated landscapes can potentially be incorporated into orangutan conservation planning. Although we emphasize that plantations have less value for overall biodiversity conservation than natural forests, they could potentially boost the chances of orangutan survival. Our findings are based on a relatively short study and various methodological issues need to be addressed, but they suggest that orangutans may be more ecologically flexible than previously thought.

Characteristic of Orangutan Habitat in Coal Mining Rehabilition Area in East Kalimantan, Indonesia

“…et al According to Ancrenaz et al (2007), bornean orangutan species at a certain degree had an ability to survive at disturbed habitat by eating alternative/fallback food available in that area. For example, when the natural food was not enough, orangutan living within and outside the palm tree plantation and they ate young palm (Yuwono et al 2007;Ancrenaz et al 2010), orangutan living at and around the pulp and paper plantation ate the bark of A mangium (Denis . et al 2010;Meijaard et al 2010), orangutan living in the area of agriculture changed their active eating time and ate the crop yield that belonged the society, like star fruit, jack fruit, durian and pete (Campbell-Smith et al 2011).…”

“…For example, when the natural food was not enough, orangutan living within and outside the palm tree plantation and they ate young palm (Yuwono et al 2007;Ancrenaz et al 2010), orangutan living at and around the pulp and paper plantation ate the bark of A mangium (Denis . et al 2010;Meijaard et al 2010), orangutan living in the area of agriculture changed their active eating time and ate the crop yield that belonged the society, like star fruit, jack fruit, durian and pete (Campbell-Smith et al 2011). Marshall and Wrangham (2007) define fallback food as foods whose use is negatively correlated with the availability of preferred foods.…”

Canopy structure drives orangutan habitat selection in disturbed Bornean forests

“…Previous conservation strategies have focused on protecting primary forest, based on the idea that orangutans are dependent on pristine forest habitat (10,11). However, recent work has found orangutans to be much more flexible in their behavior, and more resilient to anthropogenic disturbance than previously thought (12,13). For example, contrary to previously held views, orangutans travel terrestrially in all forest types but display increased terrestrial activity in both heavily disturbed and primary forest, suggesting that not only can they adapt their behavior but that anthropogenic disturbance is not necessarily the dominant driver of such behavioral adaptation (14).…”

“…Indeed, more than 70% of Bornean orangutans occur in fragmented, multiple-use, and human-modified forests, ranging from degraded forest with ongoing timber extraction to secondary forest, and even tree and oil palm plantations (13,15,16). Although it remains essential to conserve primary forest from conversion and degradation, for orangutans and many other conservation objectives, it is becoming apparent that this strategy alone is not enough to safeguard the species in the long term.…”

Restoration planning of degraded tropical forests for biodiversity and ecosystem services

“…While of less benefit for overall biodiversity, monoculture timber plantations (e.g. Acacia mangium) could still provide marginal habitat for generalist species such as orangutans (Meijaard et al, 2010a).…”