"Today, more than half of the global population lives in urban areas, up from around one-third in 1950 and projected to increase to around two-thirds in 2050."

Deforestation

Over time, forests have been cleared to create room for farming, livestock grazing, and to harvest wood for energy, industry, and building purposes. "About 2,000 years ago, 80 percent of Western Europe was forested; today the figure is 34 percent."

Habitat Loss & Fragmentation

Natural habitats are often transformed for human purposes. "For example, in Nebraska, 98 percent of the tallgrass prairie and 35 percent of wetlands have been lost, primarily due to conversion to cropland." When a species' habitat is broken into separate, unconnected areas, it leads to habitat fragmentation.

Pollution

High concentrations of vehicles, industrial operations, and energy production in urban areas produce large amounts of pollutants, including carbon dioxide, and methane. Nearby water bodies frequently become contaminated by industrial effluents, sewage, and urban runoff. 

Climate Change

Urban areas absorb more heat due to dark surfaces, creating urban heat islands with higher temperatures than rural areas. City activities also drive climate change. "Estimates suggest that urban areas are responsible for 70 percent of global CO2 emissions, with transport and buildings being among the largest contributors."

Erosion

In cities, soil erosion is a major issue caused by vegetation loss from construction, neglect, and overuse of public spaces. It lowers crop productivity and increases the risk of natural disasters like flooding.

Poor Water Quality

Paving land with concrete increases water runoff and reduces water quality by adding sediment and pollutants to rivers and streams.

Resource Depletion

Urban infrastructure needs large amounts of resources, often leading to overuse and unsustainable extraction. For instance, growing water demand stresses rivers, and lakes, causing serious environmental effects.

Biodiversity Loss

Urbanization creates disrupted habitats where invasive species can thrive and outcompete native ones.