Planetary Health Research Digest
Authors: Sam Hinsley
Journal: The Lancet Planetary Health (2021)

There is a stark contrast between the countries most responsible for climate change and those most impacted by it. International donations designated for climate change adaptation aim to address this inequity. Fair allocation should mean that the most vulnerable countries receive the most adaptation aid, but this is not necessarily the case. Florian Weiler (Central European University, Austria and Hungary) and Carola Klöck (CERI, France) used network models to look for interactions among donors in the allocation of adaptation aid: ie, are donor countries more likely to provide aid when other donors are also active in a recipient country? They observed substantial overlap of recipients between donors, and their models showed evidence that the presence of existing donors increased a recipient's chances of forming additional aid ties. Such aid concentration mirrors existing patterns in development aid and, the authors argue, fails to achieve the climate justice goals set by the international community. In Africa, more than 50% of people depend on agriculture to make a living, and about 80% of these farms are less than 2 hectares. Smallholders are particularly vulnerable to environmental stressors, and successive poor growing seasons may be enough to drive them off their land in search of other means of support. Andrew Linke (University of Utah, USA) and Andreas Forø Tollefsen (PRIO, Norway) hypothesised a link between drier than usual growing seasons and landownership in Africa. Using a combination of Demographic and Health Surveys and historical rainfall data, they found a 6·93% reduction in landownership following five consecutive dry growing seasons, with a further 1·38% decline for each additional dry growing season. Future climate change is expected to increase the frequency of dry growing seasons in Africa, suggesting that it could lead to growing landlessness and future land disputes, both of which could have major destabilising effects across the continent. Genetic diversity is crucial to species' ability to adapt to changing environments, and therefore to maintaining biodiversity as a whole. Mitochondrial genes provide a consistent way to assess genetic diversity between and within species. Spyros Theodoridis (University of Copenhagen, Denmark) and co-authors combined georeferenced sequences for the mitochondrial genes cytb and co1 and future climate scenarios to investigate the exposure of mammal genetic diversity to future environmental changes. More than half of areas with the lowest mammalian genetic diversity—including high latitude tundra, boreal forest, and temperate areas—were exposed to temperature increases higher than 2°C in all climate change scenarios. Of the most diverse areas—mainly in tropical, subtropical, and montane regions—30% faced similar temperature increases in the less sustainable scenarios, as well as losses of 5–10% of their total areas due to human activities in the same scenarios. By highlighting regions' mammalian genetic diversity and exposure to the effects of future global changes, the authors provide important information to direct future conservation efforts. A-horizon soil, or topsoil, is rich in organic carbon and is therefore important for plant growth and as a carbon sink. Over time, agricultural activities, particularly tillage, can lead to the erosion of A-horizon soils, which reduces the ability of the land to perform these functions. Evan Thaler (University of Massachusetts, USA) and co-authors used a new remote sensing method to quantify loss of A-horizon soils across agricultural land in the Corn Belt of the midwestern US. Unlike previous estimates which found no evidence for complete topsoil loss in this region, they report the complete loss of A-horizon soil from 35% (SD 11) of the total area studied. Convex hilltops were particularly severely affected, indicating the role of tillage erosion. They translate these soil losses to productivity losses of about 6%, or $2·8 billion. These results highlight the extent to which soils have been degraded in one of the most productive agricultural areas of the US, and indicate the potential benefits more sustainable soil management practices could bring.