Current and Proposed Conservation Strategies for the
Tapanuli orangutan (Pongo tapanuliensis)
Abstract
Biodiversity conservation is an increasingly important topic, and one species which
requires extensive attention is the Tapanuli orangutan (Pongo tapanuliensis). Despite
only being confirmed as a distinct species six years ago, P. tapanuliensis, with only 800
individuals in the wild, is the most endangered of all the Great Apes. Habitat loss and
fragmentation and conflict with humans has led to a rapid population decline for the
species. As such, much work has been done to prevent P. tapanuliensis from becoming
extinct. The existing conservation strategies primarily rely on the use of ecosystem
services which, though beneficial in some respects, can also hinder conservation. This
report critically evaluates the use of ecosystem services for conservation and finds that
future conservation strategies should move away from regulating and provisioning
services and instead give more attention to cultural ecosystem services.
Introduction
The only known population of Tapanuli orangutan (Pongo tapanuliensis) is located south
of Lake Toba in North Sumatra, Indonesia (Nater et al., 2017). P. tapanuliensis are
primarily found in highland forests and their entire habitat consists of just three forest
blocks in the Batang Toru region totalling 1,023 km2 (Wich et al., 2014; Meijaard et al.,
2021). Originally thought to be Sumatran orangutans (Pongo abelii), analyses of their
morphology and mitochondrial DNA confirmed that P. tapanuliensis and P. abelii were
two distinct species (Nater et al., 2017). As with the Sumatran orangutan and the
Bornean orangutan (Pongo pygmaeus), P. tapanuliensis is considered critically
endangered (Wich et al., 2019). Due to a variety of factors – such as habitat
fragmentation and poaching – the population of P. tapanuliensis is estimated to contain
no more than 800 individuals (Nater et al., 2017). As such, a thorough analysis of the
species, the threats they face, and the current conservation strategies is urgently needed
to prevent the Tapanuli orangutan from becoming extinct. This report will focus on the
role of ecosystem services in the conservation of P. tapanuliensis, offering a critical
evaluation of the current conservation strategies. In addition to this, the report will also
suggest how conservation efforts may be improved by offering additional strategies.
In order to view the current and proposed conservation strategies in the proper context,
we must first discuss the most immediate dangers faced by P. tapanuliensis. Perhaps the
most significant of these threats is the loss and fragmentation of the Tapanuli
orangutan’s habitat. As there is only one known population of P. tapanuliensis – that of
the Batang Toru region of North Sumatra – the destruction of any of its habitat poses a
severe risk to the species. The extent to which its habitat has declined over the years is
, therefore incredibly dangerous. Today, P. tapanuliensis is primarily found in areas of high
elevation – approximately 1,000 metres above sea level (Wich et al., 2014; Meijaard et
al., 2021) – leading some to believe that Tapanuli orangutans are specifically adapted for
such areas. However, based on genetic analyses and estimations of historic distribution
ranges, it is more likely that P. tapanuliensis, rather than being adapted to higher
elevated areas, was simply forced into these areas due to the destruction of lowland
forests (Meijaard et al., 2021). The estimated range of the Tapanuli orangutan in the
1890s was approximately 41,000 km2, but by 2021 that had fallen to approximately
1,000 km2; a 97% decrease. This rapid and significant decline was largely the result of the
logging and palm oil industries (UNEP, 2011; Meijaard et al., 2021). As well as leading to
decreased space and resources, this loss and fragmentation of habitat also forces P.
tapanuliensis into closer proximity to human-inhabited areas, increasing the risk of
conflict between the two species.
As a result of these factors, P. tapanuliensis is classified as critically endangered as the
population has declined by approximately 80% over the last 75 years; it is estimated that
there are no more than 800 individuals in the wild (Meijaard et al., 2021). This issue of a
population bottleneck poses a significant risk to the species; the small population size
has led to inbreeding, indicated by extensive homozygosity between individuals (Nater et
al., 2017). This lack of genetic variation limits the ability of P. tapanuliensis to adapt to
environmental changes, as well as increasing its risk of being wiped out by disease.
However, despite the significance of this issue, the effects of a genetic bottleneck occur
over a much broader timescale than that of environmental issues such as habitat
destruction (Jamieson et al., 2008). As such, the threats posed by low genetic diversity,
whilst severe, are perhaps the least urgent of the threats faced by P. tapanuliensis.
Current strategies
The first thing that must be considered when reviewing the existing conservation
strategies for Tapanuli orangutans is that they were not confirmed as a distinct species
until 2017. As such, all of the literature prior to 2017 mistakenly refers to P. tapanuliensis
as a population of Sumatran orangutans, and this may have had damaging effects. For
example, the United Nations Environment Programme (UNEP, 2011) describes the
habitat of the ‘Sumatran’ orangutan as an important cultural service due to it being a
popular tourist destination. They also refer to recreational water activities taking place
within the forests of Batang Toru. As tourism can generate income for conservation and
raise awareness of conservation issues, any negative consequences of these activities
(such as disturbing nearby orangutan populations) were presumably thought to be
negligible when it was believed the region was inhabited by Sumatran orangutans. And
whilst trade-offs such as these are not uncommon when implementing conservation
strategies (Hirsch et al., 2010), now that it is known the orangutans in the region belong
to the only known population of P. tapanuliensis, the potential disturbance to them
caused by tourism poses too great a risk.
