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Protecting proboscis monkeys from deforestation

2 January 2019

Proboscis monkey

A 10 year study of proboscis monkeys in Borneo has revealed that forest conversion to oil palm plantations is having a significant impact on the species.

Nearly half of all primate species are threatened with extinction, with habitat destruction acting as the key driving force. New research studied proboscis monkeys from 2004 to 2014, finding that the protection of swamp forests is vital for their survival.

The study led by Cardiff University, Chubu University, Hokaido University, Sun Yat-sen University, Living Landscape Alliance, the NGO HUTAN, Sabah Wildlife Department and Danau Girang Field Centre, tracked changes in population sizes over a decade, revealing significantly reduced sizes of proboscis monkey groups.

Dr Benoit Goossens, Director of Danau Girang Field Centre and Reader at Cardiff University School of Biosciences, said: “We compared population sizes from 2004 and 2014, and it revealed subtle changes, where population densities fluctuated but had neither increased nor decreased. But importantly, we discovered that the sizes of the groups were significantly reduced.

Professor Benoit Goossens

Studies on the impact of habitat changes on primate populations are limited and often based on inferences because primates are long-lived mammals with slow life cycles, and generally respond very slowly to environmental changes. Information like this is essential for developing effective management plans for long-term conservation.

Dr Benoît Goossens, Director, Danau Girang Field Centre, Reader

Mr Augustine Tuuga, Director of Sabah Wildlife Department, said: “Proboscis monkeys are endemic to the island of Borneo. They are classified as endangered and are also a Totally Protected species in Sabah. Despite these levels of protection, lowland swamp forest habitats that are important for this species are still decreasing, mainly through forest conversion to oil palm plantations.

“Our analysis of the habitat changes showed that within protected reserves, there was relatively little forest loss in the potential range of the proboscis monkey, which mainly lies 800m from riverbanks.”

“This suggests that the protection of swamp forests can contribute immensely to the sustainability of proboscis monkeys within these important habitats. However, larger losses of interior forests meant that habitats had generally become more degraded and fragmented, and this could have contributed to reduced group sizes and limited population growth,” added Dr Marc Ancrenaz, Scientific Director at the NGO HUTAN.

Dr Benoit Goossens concluded: “Although the protection of forests within the proboscis monkeys’ range had proved effective, this was not the case in unprotected forests, where 12% of the forest was lost and could eventually lead to 23% of the population being threatened.

“At least a third of these forests has been allocated for oil palm cultivation. Further efforts must be undertaken to more effectively conserve high value habitats and to restore swamp forest areas – this is vital for ensuring the survival of this endangered species.”

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