Mitigating climate change and social injustice are critical, interwoven challenges. The result of elevated greenhouse gas emissions, climate change is driven by grossly unequal emissions among individuals, socioeconomic groups, and nations. Yet its deleterious impacts disproportionately affect poor and less powerful nations, and the poor and the less powerful within each nation. This climate injustice prompts a call for mitigation strategies that buffer the poorest and the most vulnerable against climate change impacts. Unfortunately, all emissions mitigation strategies also reshape social, economic, political, and ecological processes in ways that may create climate change mitigation injusticesi.e., a unique set of injustices not caused by climate change, but by the strategies designed to stem it. Failing to stop climate change is not an answerthis will swamp all adverse impacts of even unjust mitigation in terms of the scope and scale of disastrous consequences. However, mitigation without justice will create uniquely negative consequences for the more vulnerable. The ensuing analysis systematically assesses how climate change mitigation strategies can generate or ameliorate injustices. We first examine how climate science and social justice interact within and among countries.

A document by Peter B Reich. Click on the document to view its contents.

The linkage of stomatal behavior with photosynthetic processes is critical to understanding water and carbon cycles under global change. The slope ( g1) of stomatal conductance ( gs) versus CO 2 assimilation ( Anet) serves as a proxy of the marginal water cost of carbon acquisition and the trade-off between carbon gain and water loss. Here we use g1 to assess species differences in the response of stomatal behavior to experimental climate change manipulations, asking whether generalizable patterns exist across species and climate contexts. A total of 17,727 Anet- gs measurements made in a long-term open-air experiment under ambient and +3.3°C warming, and ambient and ~40% summer rainfall reduction provided > 2,700 estimates of g1 across 21 boreal and temperate tree species. All species became more conservative in their water use (lower g1) in warming and/or reduced rainfall treatments because of lower soil moisture. In contrast to these phenotypic responses, species from warmer and drier habitats tended to have slightly higher g1 and to be the least sensitive to the decrease in soil water. Overall, both warming and rainfall reduction consistently made stomatal behavior more conservative in terms of water loss per unit carbon gain across 21 species and a decade of experimental observation.

Epiphytes have long been reported to have larger geographic ranges than terrestrial species, despite evidence of their outstanding diversity and endemism. This apparent contradiction calls for further investigation of epiphytes’ poorly understood range size patterns. Here, we address the question of whether epiphytes have larger geographic ranges than terrestrial species in the Atlantic Forest of Brazil, a global centre of epiphyte diversity. In contrasting the extent of occurrence and area of occupancy of 12,679 epiphytes and non-epiphytes at varying taxonomic scales, we found that epiphytes have among the smallest geographic ranges of flowering plants and likely a high vulnerability to species extinction. We found no evidence that epiphytism leads to differences in geographic ranges between close relatives. However, epiphytes and non-epiphytes in epiphyte-rich lineages share many diversification mechanisms and ecological adaptations (‘epiphyte-like traits’), which probably explains why both sets of species have small range sizes and high vulnerability to extinction.