Planetary health digest
Authors: Sam Hinsley
Journal: The Lancet Planetary Health (2019)

Groundwater extraction by pumping from underground aquifers is crucial to support agriculture and other human activities in areas where surface water supplies are insufficient. However, extraction often far exceeds the recharge rate of these aquifers, leading to falls in groundwater levels. As the groundwater level drops, the patterns of discharge into rivers, lakes, and other freshwater environments also change, with potentially devastating consequences for these ecosystems. Inge de Graaf, University of Freiburg, Germany, and co-authors investigated the impact of groundwater pumping on groundwater discharge, identifying where environmentally critical streamflow reductions are already occurring and where they can be expected to occur in the future. They find that these environmental flow limits have already been reached in a substantial proportion of the world's watersheds in which pumping occurs (15–21% depending on the climate projections used), and that this number is expected to grow significantly by 2050 (estimates of 42–79%). With this illustration of the scope of the challenges ahead, the authors call for the integration of groundwater requirements into any future assessment of worldwide water sources. Seafood is the most rapidly expanding food production sector and has been proposed as having a key role in sustainable diets. Existing mechanisms to encourage sustainability in the industry have largely focused on governmental regulations, market-based approaches (eg, certification), and voluntary commitment by companies. The role of financial mechanisms has been speculated on but has so far remained understudied. Using a content analysis of two leading seafood-focused media outlets, qualitative examples, and descriptive statistics of shareholder analysis, Jean-Baptiste Jouffray from the Stockholm Resiliency Centre, Sweden, and colleagues aimed to identify key financial leverage points for encouraging sustainability in the seafood sector. These leverage points focus on mainstream financial mechanisms and can be divided into actions from three types: sustainability covenants on loans from banks, stock exchanges requiring certain environmental criteria be met for a company to be listed, and shareholder activism. While these mechanisms are, by their nature, restricted to larger businesses, they could exert a powerful influence and might also be relevant to other extractive industries. The urban heat island (UHI) effect is a well known consequence of urbanisation and the resulting replacement of natural environments with constructed ones. It can have serious consequences for human health, as elevated temperatures pose direct risk for conditions such as dehydration and heat stress, as well affecting existing disorders such as cardiovascular and respiratory diseases. With the continuing growth of the world's urban population and the diversity of these cities it is important to understand the which populations are most at risk. To this end, Tirthankar Chakraborty from the Yale School of Forestry and Environmental Studies, USA, and colleagues conducted an analysis of 25 cities around the world, looking at the neighbourhood-level UHI effect and income to identify socioeconomic disparities. The results differed with city characteristics, but the majority (18 [72%] cities) had UHI effects that disproportionately affected people on lower incomes, and these effects were closely correlated with indices of urbanicity and greenness. The authors' findings suggest that city-specific measures will be needed to tackle the issue of UHIs, and that doing so could be one way to tackle the issue of health inequalities within cities. Fires in Indonesia are a major source of particulate matter pollution both within the country and in neighbouring countries in equatorial Asia. Furthermore, they represent a significant contribution to global greenhouse gas emissions, with fires in 2015 releasing an amount of CO2 equivalent to the yearly fossil fuel combustion of India or Japan. These fires are mainly from land clearance for cultivation or wildfires during drought periods, which are exacerbated by the drainage of carbon-rich peatlands. Miriam Marlier from the RAND Corporation, Santa Monica, USA, and co-authors created a decision-support tool to estimate the magnitude of fire emissions over the coming decades, their public health impacts, and the gains that could be made with various land management approaches. They report that the PM2·5 released by these fires would be responsible for an average of 36 000 excess deaths per year across Indonesia, Malaysia, and Singapore, and that the majority (>60%) of these emissions were the result of fires on peatlands. The study highlights the importance of policies to block fires in peatlands, which the authors predict could prevent two-thirds of these excess deaths. For more on seafood production see https://advances.sciencemag.org/content/5/10/eaax3324 For more on seafood production see https://advances.sciencemag.org/content/5/10/eaax3324