• Energy Research

If current trends continue, the tropical forests of the Anthropocene will be much smaller, simpler, steeper and emptier than they are today. They will be more diminished in size and heavily fragmented (especially in lowland wet forests), have reduced structural and species complexity, be increasingly restricted to steeper, less accessible areas, and be missing many heavily hunted species. These changes, in turn, will greatly reduce the quality and quantity of ecosystem services that tropical forests can provide. Driving these changes will be continued clearance for farming and monoculture forest plantations, unsustainable selective logging, overhunting, and, increasingly, climate change. Concerted action by local and indigenous communities, environmental groups, governments, and corporations can reverse these trends and, if successful, provide future generations with a tropical forest estate that includes a network of primary forest reserves robustly defended from threats, recovering logged and secondary forests, and resilient community forests managed for the needs of local people. Realizing this better future for tropical forests and people will require formalisation of land tenure for local and indigenous communities, better-enforced environmental laws, the widescale roll-out of payments for ecosystem service schemes, and sustainable intensification of under-yielding farmland, as well as global-scale societal changes, including reduced consumerism, meat consumption, fossil fuel reliance, and population growth. But the time to act is now, while the opportunity remains to protect a semblance of intact, hyperdiverse tropical forests.

The human population is expected to reach ∼9 billion by 2050. The ensuing demands for water, food and energy would intensify land-use conflicts and exacerbate environmental impacts. Therefore we urgently need to reconcile our growing consumptive needs with environmental protection. Here, we explore the potential of a land-use optimisation strategy to increase global agricultural production on two major groups of crops: cereals and oilseeds. We implemented a spatially-explicit computer simulation model across 173 countries based on the following algorithm: on any cropland, always produce the most productive crop given all other crops currently being produced locally and the site-specific biophysical, economic and technological constraints to production. Globally, this strategy resulted in net increases in annual production of cereal and oilseed crops from 1.9 billion to 2.9 billion tons (46%), and from 427 million to 481 million tons (13%), respectively, without any change in total land area harvested for cereals or oilseeds. This thought experiment demonstrates that, in theory, more optimal use of existing farmlands could help meet future crop demands. In practice there might be cultural, social and institutional barriers that limit the full realisation of this theoretical potential. Nevertheless, these constraints have to be weighed against the consequences of not producing enough food, particularly in regions already facing food shortages. ISSN:2167-8359 PeerJ, 1

Southeast Asia, which encompasses four biodiversity hotspots (Indo-Burma, Sundaland, the Philippines, and Wallacea), is a region of remarkably high biodiversity. Much of the region's flora and fauna is not found elsewhere in the world (endemic). Unfortunately, this region has been experiencing widespread and rapid deforestation and forest degradation over the last few decades, driven primarily by industrial agriculture, such as oil palm development. In this article, the authors discuss the status of key natural ecosystems and taxonomic groups. Additionally, they highlight the major threats to biodiversity as well as the challenges and opportunities for conservation in this region.

Global demands for agricultural and forestry products provide economic incentives for deforestation across the tropics. Much of this deforestation occurs with a lack of information on the spatial distribution of benefits and costs of deforestation. To inform global sustainable land-use policies, we combine geographic information systems (GIS) with a meta-analysis of ecosystem services (ES) studies to perform a spatially explicit analysis of the trade-offs between agricultural benefits, carbon emissions, and losses of multiple ecosystem services because of tropical deforestation from 2000 to 2012. Even though the value of ecosystem services presents large inherent uncertainties, we find a pattern supporting the argument that the externalities of destroying tropical forests are greater than the current direct economic benefits derived from agriculture in all cases bar one: when yield and rent potentials of high-value crops could be realized in the future. Our analysis identifies the Atlantic Forest, areas around the Gulf of Guinea, and Thailand as areas where agricultural conversion appears economically efficient, indicating a major impediment to the long-term financial sustainability of Reducing Emissions from Deforestation and forest Degradation (REDD+) schemes in those countries. By contrast, Latin America, insular Southeast Asia, and Madagascar present areas with low agricultural rents (ARs) and high values in carbon stocks and ES, suggesting that they are economically viable conservation targets. Our study helps identify optimal areas for conservation and agriculture together with their associated uncertainties, which could enhance the efficiency and sustainability of pantropical land-use policies and help direct future research efforts.

Abstract Despite the looming land scarcity for agriculture, cropland abandonment is widespread globally. Abandoned cropland can be reused to support food security and climate change mitigation. Here, we investigate the potentials and trade-offs of using global abandoned cropland for recultivation and restoring forests by natural regrowth, with spatially-explicit modelling and scenario analysis. We identify 101 Mha of abandoned cropland between 1992 and 2020, with a capability of concurrently delivering 29 to 363 Peta-calories yr− 1 of food production potential and 290 to 1,066 MtCO2 yr− 1 of net climate change mitigation potential, depending on land-use suitability and land allocation strategies. We also show that applying spatial prioritization is key to maximizing the achievable potentials of abandoned cropland and demonstrate other possible approaches to further increase these potentials. Our findings offer timely insights into the potentials of abandoned cropland and can inform sustainable land management to buttress food security and climate goals.

This data package includes the two 1-km resolution global maps of tropical mangrove forests between ~31°N and 39°S produced from the study: 1) investible mangrove blue carbon (in tCO2e ha-1y-1) and 2) profitable mangrove blue carbon (in tCO2e ha-1y-1). It also includes a sample R script to reproduce these layers and the relative country-level project development and maintenance cost estimates. Investible mangrove blue carbon: To model and produce a spatially explicit map of investible mangrove blue carbon, we first estimated the total volume of CO2e across three pools in mangrove forest areas—aboveground carbon, belowground carbon and soil organic carbon: Aboveground carbon: We used a recent global mangrove aboveground biomass model by Simard et al. 2019 to estimate the volume of aboveground carbon. We applied a stoichiometric factor of 0.475 to convert biomass estimates to carbon stock values. We also performed an uncertainty analyses to account for variability in this stoichiometric factor. We then used a conversion factor of 3.67 to convert carbon stock values to CO2e volume. Belowground carbon: We then used the aboveground biomass from Simard et al. 2019to estimate the belowground (root) biomass, following the allometric equation from Hutchison et al. 2014: Belowground biomass = 0.073 •Aboveground biomass1.32. Our belowground biomass estimations fall within the range of previously derived ratios of aboveground:belowground (root) biomass ratios. We applied the same stoichiometric factor (0.475) and conversion factor (3.67) to estimate the volume of CO2e associated with belowground biomass. Soil organic carbon: Additionally, to fully consider ecosystem mangrove carbon stock, we also utilized mangrove soil carbon stocks obtained from Sanderman et al. 2018, applying a conversion factor (3.67) to estimate the volume of CO2e. To these biomass carbon estimates, we then applied key criteria that enables certification of carbon credits under the rules of the UNFCCC, Kyoto Protocol, and the various voluntary certification standards such as the Verified Carbon Standard (VCS). Importantly, our analyses were guided by the requirements stipulated by VCS—the most widely used voluntary greenhouse gas program globally: Additionality: A major component of certification is ‘additionality’ or the amount of carbon stocks that would have been lost without the intervention of forest protection of the proposed project. To estimate additionality, we assume future rates of mangrove forest loss to follow existing patterns between the years 2000–2016. This data was obtained from Goldberg et al. 2020. This was calculated as the annualized rate of mangrove loss within each ~1 km cell. We then applied this estimated annual deforestation rate to the volume of CO2e associated with mangrove forest (calculated above), to derive the volume of CO2e that would be certifiable and thus investible under the VCS. Decay rates: We also considered the annual decay rate specific to mangrove forests [29]. This was based on two carbon pools—the belowground (root) biomass, with a decay rate of 0.20, and soil organic carbon, with a decay rate of 0.10. These values are based on median estimates from Lovelock et al. 2017, and we also performed an uncertainty analyses to account for variability in these decay rates. Buffer credits: Lastly, we also applied the VCS requirement to set aside buffer credits of 20% net change carbon stocks in each area to account for risk of non-permanence. Profitable mangrove blue carbon: To estimate the relative profitability of these mangrove blue carbon sites, we utilized the map of investible mangrove blue carbon to calculate the net present values (NPV) based on several simplifying assumptions obtained from previous studies’ published data. We first used the cost of project establishment at US$232 ha-1, based on a wide range of costs that are key to the development of a project such as project design, governance and planning, and enforcement. We also used an annual maintenance cost of US$25 ha-1, which can include aspects such as monitoring, finance and administration. Given the potential for establishment and maintenance cost to vary between countries, then weighted this cost by countries’ per capita gross domestic product (GDP) to estimate the relative cost per country. We then assumed a constant carbon price of US$5 t-1CO2e for the first five years, roughly matching the average carbon price of all avoided deforestation projects recorded by Forest Trends’ Ecosystem Marketplace reports between 2006–2018. After the first five years, we assumed a 5% price appreciation for subsequent years over a 30-years project timeframe. Based on these criteria, we calculated the NPV as well as the accumulated profits over the next 30 years, based on a 10% risk-adjusted discount rate. Using the spatially explicit NPV estimates, we excluded areas that were not financially sustainable (negative NPV), and calculated the extent, climate mitigation potential and return-on-investment within the remaining, profitable, areas.. Further details for these datasets are presented in Zeng et. al. For questions or issues on the spatial data layers, please contact Yiwen Zeng (zengyiwen@nus.edu.sg).

Large tracts of tropical rainforests are being converted into intensive agricultural lands. Such anthropogenic disturbances are known to reduce species turnover across horizontal distances. But it is not known if they can also reduce species turnover across vertical distances (elevation), which have steeper climatic differences. We measured turnover in birds across horizontal and vertical sampling transects in three land-use types of Sri Lanka: protected forest, reserve buffer and intensive-agriculture, from 90 to 2100 m a.s.l. Bird turnover rates across horizontal distances were similar across all habitats, and much less than vertical turnover rates. Vertical turnover rates were not similar across habitats. Forest had higher turnover rates than the other two habitats for all bird species. Buffer and intensive-agriculture had similar turnover rates, even though buffer habitats were situated at the forest edge. Therefore, our results demonstrate the crucial importance of conserving primary forest across the full elevational range available.