Climate change could affect agriculture in several ways including productivity, agricultural practices, environmental effects, and distribution of rural space. Additional number affected by malnutrition could rise to 600 million by 2080. Climate change could worsen the prevalence of hunger through direct negative effects on production and indirect impacts on purchasing powers. Of the 3 billion growth in population projected worldwide by the mid-21st century, the majority will be born in countries already experiencing water shortages. As the overall climate of the earth warms, changes in the nature of global rainfall, evaporation, snow, and runoff flows will be affected. Safe water sources are essential for survival within a community. Manifestations of the projected water crisis include inadequate access to safe drinking water for about 884 million people as well as inadequate access to water for sanitation and water disposal for 2.5 billion people. Sea levels could rise rapidly with accelerated ice sheet disintegration. Global temperature increases of 3–4 degrees C could result in 330 million people being permanently or temporarily displaced through flooding Warming seas will also fuel more intense tropical storms. Climate change is already transforming Ecological systems. Around one-half of the world's coral reef systems have suffered bleaching as a result of warming seas. In addition, the direct human pressures that might be experienced include overfishing which could lead to resource depletion, nutrient and chemical pollution and poor land use practices such as deforestation and dredging. Also, climate change may increase the amount of arable land in high-latitude regions by reduction of the amount of frozen lands. A 2005 study reports that temperature in Siberia has increased three degree Celsius in average since 1960, which is reportedly more than in other areas of the world. A direct effect is increase in temperature-related illnesses and deaths related to prolonged heat waves and humidity. Climate change could also change the geographic range of vector-borne, specifically mosquito-borne disease such as malaria dengue fever exposing new populations to the disease. Because a changing climate affects the essential ingredients of maintaining good health: clean air and water, sufficient food and adequate shelter, the effects could be widespread and pervasive. The report of the WHO Commission on Social Determinants of Health points out that disadvantaged communities are likely to shoulder a disproportionate share of the burden of climate change because of their increased exposure and vulnerability to health threats. Over 90 percent of malaria and diarrhea deaths are borne by children aged 5 years or younger, mostly in developing countries. Other severely affected population groups include women, the elderly and people living in small island developing states and other coastal regions, mega-cities or mountainous areas.