The effects of land-use policies on the conservation of Borneo’s endemic Presbytis monkeys

Despite supporting the highest biodiversity on Earth, tropical rainforests are undergoing intensive economic development. In particular, the island of Borneo has lost over 56 % of original lowland forest to resource extraction, fires, and illegal logging. Its rainforests contain 16 primate species, which serve as excellent ‘umbrella’ taxa for conservation initiatives. The genus Presbytis (Colobinae) is well represented across Borneo by four endemic species (P. chrysomelas; P. frontata; P. hosei, and P. rubicunda), but remains relatively understudied. Using ecological niche modelling, I calculated the distributions of the 12 Bornean Presbytis subspecies; evaluated habitat loss between 2000 and 2010, and examined the current land-use policies across remnant distributions. Subspecies experienced a mean 12.7 % (N = 12 sp.) habitat reduction over the 10 year period. 12.5 % of all habitats were allocated for conversion to oil palm and industrial tree plantations, while logging concessions accounted for a mean 26.3 % across distributions. While the current protected area networks encompassed an average 33.4 % of distributions, most PAs are underfunded, degraded and threatened by logging and mining operations. I therefore recommend priority gazetting of unallocated lands to new PAs within the distribution of Presbytis chrysomelas and Presbytis hosei sabana, which have experienced the highest forest loss in the last 10 years (22–50 %) and are critically endangered. Logging concessions appear to be at least as effective in maintaining forest cover as PAs and have the economic advantage for effective management, but may have detrimental effects to monkey populations. I recommend an urgent assessment of the effects of selective logging practices on species’ persistence, and further recommend population surveys to quantify the populations of critically endangered and data deficient subspecies.