Impacts on ecosystems and biodiversity are a prominent area of research in climate change. However, little is known about the effects of abrupt climate change and climate catastrophes on them. The probability of occurrence of such events is largely unknown but the associated risks could be large enough to influence global climate policy. Amphibians are indicators of ecosystems’ health and particularly sensitive to novel climate conditions. Using state-of-the-art climate model simulations, we present a global assessment of the effects of unabated global warming and a collapse of the Atlantic meridional overturning circulation (AMOC) on the distribution of 2509 amphibian species across six biogeographical realms and extinction risk categories. Global warming impacts are severe and strongly enhanced by additional and substantial AMOC weakening, showing tipping point behavior for many amphibian species. Further declines in climatically suitable areas are projected across multiple clades, and biogeographical regions. Species loss in regional assemblages is extensive across regions, with Neotropical, Nearctic and Palearctic regions being most affected. Results underline the need to expand existing knowledge about the consequences of climate catastrophes on human and natural systems to properly assess the risks of unabated warming and the benefits of active mitigation strategies.

This study quantifies the impacts of climate change on yields and the corresponding economic losses in six relevant crops that account for 65% of the harvested area in Mexico and are highly relevant in terms of consumption and economic value. The results show that crop yields could decrease considerably during this century, especially in the rainfed management system. Under a high-emission scenario, large reductions in yields are expected by the end of this century for both rainfed and irrigated management systems of maize (42%, 31.4%), rice (51.4%, 41.3%), sorghum (41.1%, 36.6%), soybean (59.1%, 44.9%), wheat (23.3%, 20.0%), and rainfed sugarcane (11.7%). At the national level, the present value of losses in the selected crops amounts to $37,934 million dollars, which represents about twice the current total national agricultural production of Mexico. Rainfed agriculture represents about 69% of these losses and reductions in maize yields account for almost 70% of the total losses. States such as Veracruz, Sinaloa, Tamaulipas, and Jalisco represent half of the total economic losses. However, about 16% of the aggregated losses occur in states with high levels of poverty and subsistence farming like Chiapas, Oaxaca, and Guerrero. Climate change will significantly increase the risks that already vulnerable subsistence farmers’ face in the present. Although ambitious mitigation efforts can reduce the estimated impacts in most of the crops, residual damages are considerable, and the prompt implementation adaptation strategies is required.

Land-use/cover change is the major cause of terrestrial ecosystem degradation. However, its impacts will be exacerbated due to climate change and population growth, driving agricultural expansion because of higher demand of food and lower agricultural yields in some tropical areas. International strategies aimed to mitigate impacts of climate change and land use-cover change are challenging in developing regions. This study aims to evaluate alternatives to minimize the impacts of these threats under socioeconomic trajectories, in one of the biologically richest regions in Guatemala and Mexico. This study is located at the Usumacinta watershed, a transboundary region that shares a common history, with similar biophysical properties and economic constraints which have led to large land use/cover changes. To understand the impacts on deforestation and carbon emissions of different land-management practices, we developed three scenarios (1): business as usual (BAU), (2) a reducing emissions scenario aimed to reduce deforestation and degradation (REDD+), and (3) zero-deforestation from 2030 onwards based on the international commitments. Our results suggest that by 2050, natural land cover might reduce 22.3 and 12.2% of its extent under the BAU and REDD + scenarios, respectively in comparison with 2012. However, the zero-deforestation scenario shows that by 2050, it would be possible to avoid losing 22.4% of the forested watershed (1.7 million ha) and recover 5.9% (0.4 million hectares) of it. In terms of carbon sequestration, REDD + projects can reduce the carbon losses in natural vegetation, but a zero-deforestation policy can double the carbon sequestration produced by REDD + projects only. This study shows that to reduce the pressures on ecosystems, particularly in regions highly marginalized with significant migration, it is necessary to implement transboundary land-management policies that also integrate poverty alleviation strategies.

Evidence suggests that climate change could drastically reduce Mexico's agricultural productivity with severe socio-ecological consequences. Population growth and the increasing demand of resources will exacerbate these impacts. Focusing on rainfed maize production, we evaluate the socio-ecological risk that municipalities currently face and how climate change could modify it. Municipalities were classified based on their biophysical and socioeconomic traits like temperature, precipitation, population, gross domestic product, marginalization, and agricultural subsidies. The study identifies municipalities that would face higher risk under climate change conditions, and it evaluates whether increases in agricultural subsidies could be effective for reducing the farmers' future risk. Our results show that during the 2010's, 36.8% of the municipalities and 15% of the population were at very high and high risk, respectively. By 2070, under a high-warming scenario these figures increase to 56.5 and 18.5%. We find that a generalized augment in agricultural subsidies is not enough to compensate for the effects of climate change on the socio-ecological risk of rainfed maize producers. We suggest that transformative adaptation is required for managing the agricultural risk that socio-ecological systems experience under climate change conditions. Such adaptation strategies should include poverty alleviation, promotion of resistant and native varieties of crops, capacity building to improve management and water use, sustainable technification, and soil restoration.

Rising temperatures can lead to the occurrence of a large-scale climatic event, such as the melting of Greenland ice sheet, weakening the AMOC and further increasing dissimilarities between current and future climate. The impacts of such an event are still poorly assessed. Here, we evaluate those impacts across megadiverse countries on 21,146 species of tetrapods and vascular plants using the pessimistic climate change scenario (RCP 8.5) and four different scenarios of Greenland’s ice sheet melting. We show that RCP 8.5 emission scenario would lead to a widespread reduction in species’ geographic ranges (28–48%), which is projected to be magnified (58–99%) with any added contribution from the melting of Greenland. Also, declines in the potential geographical extent of species hotspots (12–89%) and alterations of species composition (19–91%) will be intensified. These results imply that the influence of a strong and rapid Greenland ice sheet melting, resulting in a large AMOC weakening, can lead to a faster collapse of biodiversity across the globe.