Key messages:

• The Congo Basin is rich in biodiversity and stores an estimated 25%-30% of the worlds tropical forest carbon stocks. As agricultural land becomes increasingly scarce in Southeast Asia, and regulatory pressures continue to intensify, the Congo Basin could become the next frontier for oil palm expansion. Most of the roughly 280 million hectares (Mha) of additional land suitable for oil palm in the Congo Basin are found in the Democratic Republic of Congo (60%), Cameroon (11%) and the Republic of Congo (10%).
• Many heavily forested countries in the Congo Basin are setting national targets to increase production to meet national and regional demands. Land area allocated to oil palm increased by 40% in the Congo Basin and five additional top-producing countries in Africa between 1990 and 2017. Without intervention, future production increases in the region will likely come from expansion rather than intensification due to low crop and processing yields, possibly at the expense of forest.
• Sustainability strategies initiated by companies and aimed at certifying palm oil mills are unlikely to be effective at curbing deforestation in the Congo Basin. Smallholder farmers are an engine of growth in the regions palm oil sector, and recent evidence suggests they are actively clearing forest to expand. Because of the proliferation of non-industrial processing facilities (artisanal mills), a substantial fraction of the palm oil produced by smallholders never passes through a company's jurisdiction. Smallholders are also disadvantaged by power imbalances and limited access to technical and financial resources. Including smallholders in sustainability strategies offers opportunities to achieve multisectoral goals.
• Recommendations to improve the sustainability of the palm oil sector in the Congo Basin include (1) improving access to finance for smallholders and non-industrial mill managers; (2) implementing policies to safeguard natural resources and facilitate access to appropriate market opportunities that offer incentives to prevent future deforestation; (3) intensifying production by replanting aging plantations, rehabilitating abandoned plantations with disease-resistant and high-yielding varieties, and increasing fertilization, without further expansion into high conservation value or high carbon stock forest areas; and (4) improving processing capacity and extraction rates by upgrading mill technologies. Sustainable palm oil development in the Congo Basin will require careful consideration of the governance, institutional, environmental and socioeconomic factors that underpin the complex regional supply chains.

Understanding the causes of economic inequality is critical for achieving equitable economic development. To investigate whether global warming has affected the recent evolution of inequality, we combine counterfactual historical temperature trajectories from a suite of global climate models with extensively replicated empirical evidence of the relationship between historical temperature fluctuations and economic growth. Together, these allow us to generate probabilistic country-level estimates of the influence of anthropogenic climate forcing on historical economic output. We find very high likelihood that anthropogenic climate forcing has increased economic inequality between countries. For example, per capita gross domestic product (GDP) has been reduced 17–31% at the poorest four deciles of the population-weighted country-level per capita GDP distribution, yielding a ratio between the top and bottom deciles that is 25% larger than in a world without global warming. As a result, although between-country inequality has decreased over the past half century, there is ∼90% likelihood that global warming has slowed that decrease. The primary driver is the parabolic relationship between temperature and economic growth, with warming increasing growth in cool countries and decreasing growth in warm countries. Although there is uncertainty in whether historical warming has benefited some temperate, rich countries, for most poor countries there is >90% likelihood that per capita GDP is lower today than if global warming had not occurred. Thus, our results show that, in addition to not sharing equally in the direct benefits of fossil fuel use, many poor countries have been significantly harmed by the warming arising from wealthy countries’ energy consumption.

Millions of people worldwide are absent from their country’s census. Accurate, current, and granular population metrics are critical to improving government allocation of resources, to measuring disease control, to responding to natural disasters, and to studying any aspect of human life in these communities. Satellite imagery can provide sufficient information to build a population map without the cost and time of a government census. We present two Convolutional Neural Network (CNN) architectures which efficiently and effectively combine satellite imagery inputs from multiple sources to accurately predict the population density of a region. In this paper, we use satellite imagery from rural villages in India and population labels from the 2011 SECC census. Our best model achieves better performance than previous papers as well as LandScan, a community standard for global population distribution.

Reconciling higher freshwater demands with finite freshwater resources remains one of the great policy dilemmas. Given that crop irrigation constitutes 70% of global water extractions, which contributes up to 40% of globally available calories (1), governments often support increases in irrigation efficiency (IE), promoting advanced technologies to improve the “crop per drop.” This provides private benefits to irrigators and is justified, in part, on the premise that increases in IE “save” water for reallocation to other sectors, including cities and the environment. Yet substantial scientific evidence (2) has long shown that increased IE rarely delivers the presumed public-good benefits of increased water availability. Decision-makers typically have not known or understood the importance of basin-scale water accounting or of the behavioral responses of irrigators to subsidies to increase IE. We show that to mitigate global water scarcity, increases in IE must be accompanied by robust water accounting and measurements, a cap on extractions, an assessment of uncertainties, the valuation of trade-offs, and a better understanding of the incentives and behavior of irrigators.