driver of water stress during the next two Exacerbating Food and Water Insecurity. decades. As precipitation declines or becomes Changing precipitation patterns, rising tem- more erratic, population growth, economic peratures, increased extreme weather events, development, and continued ine昀케cient irri- and saltwater intrusion into soil and water gation and agricultural practices will increase systems from rising seas and storm surges are demand. In many river basins, upstream likely to exacerbate food and water insecu- countries are building dams and altering water rity in some countries during the next two sources with little or no consultation with their decades. Regions that remain dependent on downstream neighbors, such as the Grand rain-fed agriculture will be particularly vul- Ethiopian Renaissance Dam, increasing the nerable, such as Sub-Saharan Africa, Central risk of con昀氀ict. America, some areas of Argentina and Brazil, Pollution. Although air and water pollution parts of the Andean region, South Asia, and have decreased in many high-income coun- Australia. By contrast, some higher latitude tries since a peak in the 20th century, they regions such as Canada, northern Europe, and continue to grow globally as the number of Russia may bene昀椀t from global warming by middle-income countries has increased; for lengthened growing seasons. instance, 80 percent of industrial and munic- Fisheries are also under threat from severe ipal wastewaters are discharged untreated over昀椀shing that climate change will further into waterways. Similar to other environmen- stress through oxygen depletion, rapid warm- tal factors, air pollution and climate change ing, and ocean acidi昀椀cation. Fishermen have in昀氀uence each other through complex interac- to go further to catch fewer and smaller 昀椀sh, tions in the atmosphere. Climate change will potentially venturing into the territorial waters lead to more stagnation events—stationary of other countries. In addition, warming ocean domes of hot air that can cause air pollutants temperatures threaten to kill many more coral to get trapped and persist in the lower atmo- reefs—already they have declined by 30 to 50 sphere—and will worsen air quality by increas- percent, and at 1.5°C warming, they could de- ing the frequency of wild 昀椀res. cline by 70 to 90 percent—further threatening 昀椀shing and tourism industries. ERODING HUMAN SECURITY Threats to Human Health. Decreased water, The physical impacts of a warmer world, air, and food quality, along with changes in combined with environmental degradation, disease vectors and water-borne pathogens, are likely to lead to an array of human secu- all threaten human life. Death rates from rity challenges, primarily but not exclusively in developing countries in the near term. pollution vary signi昀椀cantly across the world— typically highest in middle-income countries According to a 2018 study, 36 percent of cities in East and South Asia. In addition, extreme globally face acute environmental stress from weather and disasters often kill people and droughts, 昀氀oods, and cyclones; climate change disrupt health infrastructure and prevent will add to these. These challenges will com- access to care. Climate change is expected pound one another in coming years; as ex- to change the geographic range and in some treme events become more intense and more frequent, societies may struggle to recover cases frequency of disease outbreaks a昀昀ecting from one event before the next one hits. humans, animals, and plants, including those A MORE CONTESTED WORLD 35