Tropical forest fragments contribute to species richness in adjacent oil palm plantations

Abstract

In Southeast Asia, large-scale conversion of rainforest to oil palm plantations is one of the major causes of biodiversity declines. Recommendations for reducing species losses and increasing the sustainability of palm oil production advocate the retention of natural forest patches within plantations, but there is little evidence for the effectiveness of this strategy. Here, we examine to what extent rainforest remnants with different characteristics contribute to biodiversity within surrounding plantations. We sampled ground-dwelling ants in Sabah (Malaysian Borneo) using unbaited pit-fall traps along 1.km transects spanning forest-plantation ecotones of 10 forest fragments (area 5. ha-500. ha) and two continuous forest sites which bordered plantations. Ant species richness in plantations varied according to richness in adjacent forest fragments, which increased with fragment size. A trend of declining species richness in plantations with distance from the forest ecotone was consistent with spillover of forest species into plantations adjacent to forest remnants. Ant assemblages in plantations also contained more carnivorous species adjacent to large forest fragments, suggesting large fragments may have benefits for pest control in plantations, as well as benefits for local biodiversity. Our results indicate that large forest fragments support distinctive ant assemblages and increase diversity within the planted area, but small fragments (<~200. ha) contribute little to plantation diversity. Thus retaining large fragments of forest may help mitigate the loss of species within oil palm plantations.

Biodiversity of leaf-litter ants in fragmented tropical rainforests of Borneo: the value of publically and privately managed forest fragments

“…Previous studies of invertebrates in Sabah indicated that even relatively small VJRs supported populations of forest-dependent species that would not otherwise be able to persist in the agricultural landscape (Benedick et al 2006 ;Hill et al 2011 ). This contrasts with data indicating that HCVs supported few species of forest birds or ants (Edwards et al 2010 ;Lucey et al 2014 ). These studies suggest a qualitative difference in the conservation value of these different types of forest fragment, but direct comparisons have previously been lacking.…”

“…In contrast to oil palm, we found that VJRs supported 78 % of the species sampled at control sites (calculated from data in Fig. 3 ), supporting previous evidence that such forest remnants make an important contribution to biodiversity within agricultural landscapes (Benedick et al 2006 ;Lucey et al 2014 ). However, HCVs supported only 22 % of the species recorded at control sites, which is only slightly higher than the proportion of forest species recorded within the oil palm itself (19 %; Fayle et al 2010 ).…”

“…Lucey et al ( 2014 ) found that fragments can contribute to plantation diversity through spillover effects but also concluded that small (<200 ha) fragments provided few biodiversity benefits. These data call into question the effectiveness of small poor-quality HCVs in enhancing biodiversity or providing ecosystem services within plantations.…”

“…In tropical regions, the conversion of forests to agricultural crops, often grown in monoculture, is a major threat to biodiversity, and reducing biodiversity losses in landscapes dominated by agriculture is a critical conservation concern (Tilman et al 2001 ;Sodhi et al 2010 ;Laurance and Edwards 2011 ). In view of the rapid rates of expansion of farmland and agroforestry in tropical regions and the small proportion of formally protected natural and semi-natural forest, attention has recently focused on the potential for privately owned or managed remnants of forest within agricultural crops to contribute to biodiversity conservation (Scherr and McNeely 2008 ;Koh et al 2009 ;Lucey et al 2014 ). However, whilst the value of such an approach has been evaluated for a range of agricultural systems in the neotropics (Tarabelli et al 2005 ;Chan and Daily 2008 ;Muñoz et al 2013 ), there are few such data for other tropical regions.…”

Can Riparian Forest Buffers Increase Yields From Oil Palm Plantations?

“…Preserving natural forest within plantation-dominated landscapes can help reduce carbon emissions by limiting deforestation and help maintain tropical ecosystem functioning that is otherwise lost in an oil palm monoculture (Larsen et al, 2005;Memmott et al, 2007;Morris, 2010). Because protected areas can only safeguard biodiversity if animals are able to move between forest patches through dedicated habitat corridors (Bruford et al, 2010;Gregory et al, 2014), riparian buffers can support some terrestrial biodiversity by serving as sanctuaries for forest-dependent species (Evans et al, 2017;Lucey et al, 2014;Turner & Corlett, 1996) and by offering continuous habitat pathways between fragments of forest matrix. Maintaining natural riparian cover along tropical rivers may help protect aquatic biodiversity by reducing the severity of impacts on freshwater ecosystems from otherwise total conversion of floodplain forest (Chellaiah & Yule, 2018;Mander et al, 2005;Naiman et al, 2010).…”