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Concern about the human impact of climate change has led to predictions of how people living in areas vulnerable to drought, flood, and temperature changes will respond to such events. Early studies warned that climate change would lead to dramatic increases in human migration as households became unable to adapt to the impacts of climate change. More recently, empirical studies focused on observed climate events and trends have documented how migration flows vary as a function of both the severity of the event and the ability of the household to migrate, among other factors. In this paper, we provide a systematic review of this literature, based on a conceptual framework in which climate shocks (e.g., drought, floods, or temperature extremes) affect (a) household capability to migrate, by depleting household resources necessary for migration, and (b) household vulnerability in staying, by increasing the risk that a household falls (further) into poverty. In combination, these factors help explain four key patterns seen in the empirical literature: (1) climate-induced migration is not necessarily more prevalent among poorer households; (2) climate-induced migration tends to be more prevalent for long-distance domestic moves than local or international moves; (3) slow-onset climate changes (such as droughts) are more likely to induce increased migration than rapid-onset changes (such as floods); and (4) the severity of climate shocks impacts migration in a nonlinear fashion, with impacts influenced by whether the capability or vulnerability channel dominates.

A large-scale treatment–control meta-analysis of US fisheries provides evidence that the implementation of catch shares extend fishing seasons by slowing the race to fish. No catch to sharing fish In fisheries, the competitive race to fish reduces fishing season length, threatens fish stocks and leads to ecological damage, economic waste and safety risks. Catch shares—whereby fishermen, fishing vessels or cooperatives are allocated a portion of the total allowable catch—are thought to slow the race to fish, but evidence to date has been limited to individual fisheries. In this meta-analysis, Martin Smith and colleagues show that the beneficial effect of catch shares on the race to fish holds true across 39 fisheries in the US. They suggest that these findings can inform the current debate over the expansion of market-based regulatory measures, such as catch shares, in fisheries. In fisheries, the tragedy of the commons manifests as a competitive race to fish that compresses fishing seasons, resulting in ecological damage, economic waste, and occupational hazards 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 . Catch shares are hypothesized to halt the race by securing each individual’s right to a portion of the total catch, but there is evidence for this from selected examples only 2 , 9 . Here we systematically analyse natural experiments to test whether catch shares reduce racing in 39 US fisheries. We compare each fishery treated with catch shares to an individually matched control before and after the policy change. We estimate an average policy treatment effect in a pooled model and in a meta-analysis that combines separate estimates for each treatment–control pair. Consistent with the theory that market-based management ends the race to fish, we find strong evidence that catch shares extend fishing seasons. This evidence informs the current debate over expanding the use of market-based regulation to other fisheries.

Mismanagement threatens the productivity and sustainability of an increasing number of capture fisheries globally, hindering these resources' ability to contribute to socio-economic and environmental outcomes such as those embodied in the Sustainable Development Goals. Using Pakistan as a case study, we assess the contribution that improved management of Pakistan's marine fisheries can make to development through economic growth, productivity, employment, and resource sustainability. Using a bioeconomic model based on a recent stock assessment, we find large projected benefits of fisheries reform relative to business as usual. However, projected production volume is not higher than current output, which is inflated by ongoing overfishing. Aquaculture is found to have potential for substantial and complementary socioeconomic benefits. We highlight how Pakistan's fisheries mirror global trends of plateauing wild capture and falling productivity and suggest key policy changes and investments along the value chain that can underpin more productive and sustainable fisheries in this context.

Mitigating climate change cost-effectively requires identifying least-cost-per-ton GHG abatement methods. Here, we estimate and map GHG abatement cost (US$ per tCO 2 ) for two common reforestation methods: natural regeneration and plantations. We do so by producing and integrating new maps of implementation costs and opportunity costs of reforestation, likely plantation genus and carbon accumulation by means of natural regeneration and plantations, accounting for storage in harvested wood products. We find natural regeneration (46%) and plantations (54%) would each have lower abatement cost across about half the area considered suitable for reforestation of 138 low- and middle-income countries. Using the more cost-effective method at each location, the 30 year, time-discounted abatement potential of reforestation below US$50 per tCO 2 is 31.4 GtCO 2 (24.2–34.3 GtCO 2 below US$20–100 per tCO 2 )—44% more than natural regeneration alone or 39% more than plantations alone. We find that reforestation offers 10.3 (2.8) times more abatement below US$20 per tCO 2 (US$50 per tCO 2 ) than the most recent IPCC estimate. It is important to understand the cost-effectiveness of natural regeneration and plantations, which are common reforestation methods for mitigation. The authors estimate and map abatement costs for the two approaches across low- and mid-income countries, helping to guide reforestation initiatives.