Urban heat islands are caused by a combination of factors, including the presence of buildings and pavement, which absorb and release heat, and the lack of vegetation, which provides shade and cools the air.

Buildings and pavement absorb and release heat, vehicles emit heat from their engines, and industrial activities generate heat as a byproduct of their processes.

Urban heat islands increase the temperature of water bodies, which can lead to a decrease in dissolved oxygen levels and an increase in the levels of pollutants, such as heavy metals and nutrients.

Urban heat islands can cause fish kills by increasing the temperature of water bodies to levels that are lethal to fish. They can also lead to the loss of aquatic vegetation, which provides food and habitat for aquatic organisms. Additionally, urban heat islands can increase the abundance of harmful algal blooms, which can produce toxins that are harmful to aquatic organisms and humans.

Planting trees and other vegetation can provide shade and cool the air. Using reflective materials on buildings and pavement can reduce the amount of heat that is absorbed and released. Installing green roofs and walls can also help to cool buildings and reduce the amount of heat that is released into the atmosphere.