Overconsumption, or people consuming resources faster than they can be replenished, is the main cause of resource depletion. Overpopulation, industrial and technological development, erosion, deforestation, over-fishing, irrigation, mining and pollution all contribute to the problem as well.
The rate at which people consume natural resources for food, for shelter, to generate energy and to manufacture products is unsustainable. Natural resources include groundwater, forests, soil, fossil fuels and marine animals. In addition to direct consumption, the effects of pollution and climate change endanger resources. For example, the glaciers that feed several major rivers are melting; this could lead to drought in the future.
Overpopulation not only increases food consumption but also escalates the need for shelter and living space. Clearing forests to create space for farms and developing urban areas leads to deforestation, and construction consumes mineral resources such as sand, gravel and crushed stone. Deforestation often leads to erosion and soil depletion, and some farming practices introduce toxins to the soil and deplete water reserves. Industries expand to meet the demands of the growing world population, consuming increasing amounts of resources.
Reusing nonbiodegradable items, such as shopping bags and glass bottles, decreases the amount of waste that goes to landfills, lowers the demand for new products and limits the consumption of raw materials. Recycling similarly conserves resources.