Consistent patterns of common species across tropical tree communities

Trees structure the Earth's most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1-6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth's 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world's most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.

Land-use Decisions in Complex Commons: Engaging Multiple Stakeholders through Foresight and Scenario Building in Indonesia

In the midst of global change uncertainties, Indonesian spatial planning authorities are developing 20-year strategies. However, the lack of collaborative engagement of stakeholders and unclear methodology around using futures studies in addressing land management undermine such plans and affect environmental governance. A crucial question is how to link a future-oriented process with governance transformation processes, particularly related to land-use planning and management. To address this issue, we used a co-elaborative scenario-building approach, referred to as participatory prospective analysis (PPA), to facilitate the creation of local multistakeholder platforms considering future-oriented perspectives. The PPA design combines equally the knowledge of local communities, technical experts and decision-makers, and was applied in a series of sequential multistakeholder workshops in two regencies in Indonesia, followed by public consultations on the main results. In both regencies, participants agreed on a common topic related to spatial planning in their jurisdiction to be explored with a 20-year time horizon. They reached consensus on relevant variables, analyzed their dependence/influence, and developed several plausible yet contrasting scenarios for land management and road maps with guidelines for the implementation of desired outcomes. The PPA approach stimulated stakeholder engagement and ensured that more local voices were not only heard but also duly included in the process. It allowed participants to consider strategies that would otherwise have been less readily accepted by their respective organizations. It showed that it is possible to improve existing spatial planning processes in Indonesia by integrating tools for a more inclusive and long-term future-oriented collaborative approach.

Ecosystem Services and Biodiversity in a Rapidly Transforming Landscape in Northern Borneo

Because industrial agriculture keeps expanding in Southeast Asia at the expense of natural forests and traditional swidden systems, comparing biodiversity and ecosystem services in the traditional forest–swidden agriculture system vs. monocultures is needed to guide decision making on land-use planning. Focusing on tree diversity, soil erosion control, and climate change mitigation through carbon storage, we surveyed vegetation and monitored soil loss in various land-use areas in a northern Bornean agricultural landscape shaped by swidden agriculture, rubber tapping, and logging, where various levels and types of disturbance have created a fine mosaic of vegetation from food crop fields to natural forest. Tree species diversity and ecosystem service production were highest in natural forests. Logged-over forests produced services similar to those of natural forests. Land uses related to the swidden agriculture system largely outperformed oil palm or rubber monocultures in terms of tree species diversity and service production. Natural and logged-over forests should be maintained or managed as integral parts of the swidden system, and landscape multifunctionality should be sustained. Because natural forests host a unique diversity of trees and produce high levels of ecosystem services, targeting carbon stock protection, e.g. through financial mechanisms such as Reducing Emissions from Deforestation and Forest Degradation (REDD+), will synergistically provide benefits for biodiversity and a wide range of other services. However, the way such mechanisms could benefit communities must be carefully evaluated to counter the high opportunity cost of conversion to monocultures that might generate greater income, but would be detrimental to the production of multiple ecosystem services.