Deforestation: As local populations grow, people clear forests to make room for crops. In addition to more food, growing populations need more wood for cooking and construction. The Petén region in Guatemala has grown from 21,000 people in 1960 to more than 600,000 today. At the current rate of destruction, Petén’s forests will be gone by 2015.
Water Scarcity: Demand for fresh water is directly proportional to population size where advanced delivery systems are not available. Agriculture uses as much as 90 percent of water resources in some drier regions of the world. Already, 1.6 billion people lack access to safe drinking water. Another 2.6 billion do not have adequate sanitation. The water table under Yemen—which has one of the highest population growth rates in the world, at 2.9 percent—is declining by one to twelve meters per year. At this rate, water supply to the capital, Sanaa, could run out by the year 2025.
Food Shortages: Each year, the world population grows by about 83 million people. Yet, global grain productivity is increasing at a rate of only 1.3 percent each year, down from 2.1 percent from 1950 to 1990. Per capita cropland has halved since 1960.
Overfishing: Today, about half of the world’s population lives within 120 miles of the coast. The coastal population is projected to increase by about 35 percent between 1995 and 2025. Seafood is the main source of protein for one-sixth of the world’s population, or almost 1.2 billion people (most of them coastal dwellers). Fisheries around the world are collapsing because of the demands placed on them by a growing population with rising incomes. The Atlantic bluefin tuna population has declined nearly 90 percent since 1970, due to overfishing.
Sprawl: More than half of the world population is now urban. As cities grow, they spread into land previously undeveloped or used for agriculture. In the process, wildlife habitats are destroyed and valuable farmland is lost. Sprawl forces people to commute to city centers from longer distances, increasing traffic congestion and reducing air quality. Cities with much sprawl, such as Atlanta, often have poor air quality during the hot summer months. Half of all smog-forming emissions in Atlanta come from the tailpipes of cars.
Habitat Loss/Species Extinction: As human populations sprawl, wildlife habitats are ruined. In the Philippines, less than 10 percent of the original vegetation survives today. As a result, two species native to the Philippines have already gone extinct (Cebu Warty Pig and Panay Giant Fruit Bat), and more than 150 endemic species of birds, mammals, and amphibians are threatened. Biologist E.O. Wilson believes that if habitat destruction by humans continues, half of all plant and animal species currently present on Earth may be extinct by the year 2100. Worldwide, 51 percent of reptiles, 52 percent of insects, and 72 percent of flowering plants are threatened, including many of the plant species used to make medicines.
Waste: Even the most conscientous consumers produce household waste and contribute indirectly to commercial waste. Residents of Lake County, Illinois produced 1.26 million tons of solid waste in 2008. Population growth is projected to cause waste to rise to 1.4 million tons by 2020. The county’s landfills are rapidly filling up and could reach capacity in the next ten years.
Pollution: Many human activities (farming, manufacturing, construction) cause air, water, and soil pollution. In China, the volume of livestock and poultry manure from meat production increased from 3.8 billion tons in 2000 to 4.8 billion tons in 2008. The manure releases massive amounts of phosphorus and nitrogen into the water supply. Runoff from animal waste caused a dangerous blue-green algae outbreak in the lake in Jiangsu province that supplies fresh water to its residents.
Climate Change: American and global per capita carbon emissions have remained steady since the 1970s. Since then, the world’s population has almost doubled, from 3.5 billion to over 6.9 billion. The rise in annual carbon emissions from fossil fuels has followed the same trend, rising from 4 billion tons in 1970 to 8.4 billion tons in 2009. Climate change disrupts the lives of the poorest people most—those who live in the least developed countries. They must walk farther to fetch fresh water, suffer stronger tropical storms, and endure crop failures due to drought.
Natural Disasters: Urban population centers located on fault lines or in hurricane-prone coastal areas are growing rapidly, endangering more people with deadly natural disasters. High population density, especially in cities where urban buildings are poorly constructed, increases the number of casualties from natural disasters like the Haiti earthquake, which killed as many as 300,000. Cities located along major fault lines, like Istanbul, where the population has risen by more than 9 million in the past 50 years, are major disasters waiting to happen.