Understanding Urbanization: How Urban Growth Affects Ecosystems and Forests

When forests are cleared and land is developed, wildlife habitat is profoundly altered — or lost altogether. This can result in local extinctions of species that rely on specific conditions to survive, shifting population dynamics, increased competition from invasive species, higher stress and mortality rates, and more. Species that live in altered environments are also more vulnerable to fire, pests, and disease.

Urbanization creates a condition called urban stream syndrome. Increasing storm water runoff, which is caused by the flow of stormwater over impervious surfaces (such as pavement), can alter natural stream flows, change water temperatures, alter the morphology of water features in the landscape, change the quality and quantity of water resources, and more.

Overburdened urban infrastructure, such as sewer lines, septic systems, and wastewater treatment overflows (or lack of), can add nutrients and organic contaminants (such as pharmaceutical drugs, caffeine, detergents, etc.) to water features. These contaminants can have a profound effect on aquatic ecosystems — and the flora and fauna that rely on them. 

According to the IPCC, in 2020, the world’s urban areas contributed about ¾ of all carbon dioxide equivalent emissions that year. At the same time, urban dwellers are increasingly vulnerable to the impacts of climate change, including rising sea levels, increased precipitation, flooding, intensifying cyclones and storms, and periods of extreme temperatures.

As of 2020, there were 31 megacities (cities with populations exceeding 10 million people) and 987 smaller cities (populations between 500,000 and five million people). By 2030, there will be over 41 megacities and 1,290 smaller cities. Building new cities requires massive amounts of raw materials like sand, metals, and wood. 

Urban heat islands are areas within urban and suburban environments that experience elevated temperatures — especially when compared to rural areas. When homes, businesses and industrial buildings are built close together, they generate, trap and store heat, which significantly increases surrounding air temperatures. In addition to stressing the health of city dwellers (people, wildlife, and plant life), the urban heat island effect can alter precipitation patterns, increase ozone production, and modify biogeochemical processes.