Deforestation and forest degradation in the tropics is a major source of global greenhouse gas (GHG) emissions. The tropics also harbour more than half the world's threatened species, raising the possibility that reducing GHG emissions by curtailing tropical deforestation could provide substantial co-benefits for biodiversity conservation. Here we explore the potential for such co-benefits in Indonesia, a leading source of GHG emissions from land cover and land use change, and among the most species-rich countries in the world. We show that focal ecosystems for interventions to reduce emissions from deforestation and forest degradation in Indonesia do not coincide with areas supporting the most species-rich communities or highest concentration of threatened species. We argue that inherent trade-offs among ecosystems in emission reduction potential, opportunity cost of foregone development and biodiversity values will require a regulatory framework to balance emission reduction interventions with biodiversity co-benefit targets. We discuss how such a regulatory framework might function, and caution that pursuing emission reduction strategies without such a framework may undermine, not enhance, long-term prospects for biodiversity conservation in the tropics.

Impacts of oil palm plantation agriculture on biodiversity have proven severe, leading to increased human-wildlife conflict, homogenization of structurally and species diverse ecosystems, and destruction of habitat for globally threatened species. Growing international demand is likely to drive further expansion of this strategic commodity in producer countries. In response, a diverse set of tools and approaches with significant potential to mitigate future impacts have been developed and are being widely applied throughout Southeast Asia, the global centre of palm oil production. This paper aims to profile these mitigation tools, beginning first with a brief review of the documented biodiversity impacts of oil palm, followed by a description of conceptual frameworks for mitigation, and a critique of five emerging mitigation tools: (1) the High Conservation Value (HCV) approach, (2) land-use advocacy, (3) carbon offsets (4), biodiversity banking and (5) enhanced regulation and enforcement. A feature shared by all is the essential role played by civil society in the development and successful implementation of these tools. We conclude by highlighting further research needs and/or activist efforts most likely to yield lasting positive impacts to redirect the location, size and shape of the oil palm 'biodiversity footprint'.

Effective corporate social responsibility (CSR) is becoming mainstream strategic business planning for the oil palm industry. At its core, CSR aims to align business values with the needs and expectations of a broader range of stakeholders, beyond just investors and shareholders. In oil palm, this entails taking responsibility for social and environmental impacts, often beyond what is required by law, to build social and environmental capital in pursuit of a local "license to operate." Third-party certification standards are a popular tool for guiding and monitoring the impact of CSR programs and have taken root in oil palm through the multi-stakeholder Roundtable on Sustainable Palm Oil (RSPO). Eight years running, the RSPO has made substantial inroads to improve the environmental and social performance of Southeast Asia's largest and fastest growing plantation industry. Yet serious challenges remain for RSPO to mainstream environmentally sustainable and socially responsible practices throughout the supply chain. Based on experiences working with multi-stakeholder groups to implement RSPO, including industry, government, local communities, and NGOs, we highlight areas where change is required not only among growers but also the broader RSPO membership to build on recent achievements and accelerate progress. Major challenges include (1) improving corporate governance of plantation companies to translate boardroom CSR decisions into conservation actions on the ground; (2) pushing RSPO member processors, traders, manufacturers, and retailers, who profit from palm oil, to share the cost burden of implementing sustainability, (3) strengthening NGO partnerships with companies to provide the social and environmental expertise companies require but still lack, and (4) creating a more supportive regulatory structure in producer countries to implement sustainability. Challenges to RSPO progress can be overcome, but will require coordinated action to ensure that the scale and pace of change is sufficient to deliver long-term benefits for the environment before it is too late.

Riparian forests are often the last remaining areas of natural vegetation in agricultural and plantation forestry landscapes. Covering millions of hectares of land in Indonesia, industrial pulpwood plantations have rapidly replaced native forests. Our study aimed to better understand the conservation importance of linear remnants of riparian forest by examining their use by larger (>1 kg) mammal species. Our study site was located within an extensive acacia (Acacia mangium) plantation adjoining Tesso Nilo National Park in Sumatra, Indonesia. Camera traps were used to detect mammals at 57 sites to assess the effects of corridor design and land cover covariates and species behavioral traits on mammal habitat use of four linear riparian forests. We recorded 17 species (including one International Union for Conservation of Nature [IUCN] Critically Endangered, two Endangered, and four Vulnerable) in riparian forests inside the plantation, including the Sumatran tiger (Panthera tigris sumatrae), Malay tapir (Tapirus indicus), and sun bear (Helarctos malayanus). Some threatened species were only detected in the park buffer zone. Species varied in their responses to riparian forests, but distance to the national park, remnant width, and percent forest cover around the camera site were common predictors of remnant use. Many mammal species used riparian forests regardless of whether they were surrounded by intact acacia forests or recently cleared land. Our results indicate that linear remnant riparian forests 200 m in width can facilitate local (< 4 km) movements of many large mammal species in Sumatra, but wider riparian remnants would likely be more effective at promoting mammal movements over longer distances.

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