Although climate change is happening at a global scale, its consequences affect communities and individuals at the local level.
Climate change directly affects the health of both human communities and urban forest ecosystems, and there are many interactions. It’s important to understand how climate change could affect the communities where you live and work in order to take action.
| Climate Impact | Potential Impacts on Urban Forests | Potential Impacts on People and Communities | How Urban Forests Reduce Impacts on People and Communities |
|---|---|---|---|
| Warmer temperatures and more days with extreme heat | > Physiological stress on trees > Range expansion of pests, disease, and invasive plant species in response to warmer conditions > Potentially increased production of volatile organic compounds | > Heat stress leading to illness or mortality > More low air quality days that exacerbate asthma, cardiovascular, and other illnesses > Increased energy utility demand for cooling and peak use failure | > Reduce extreme heat by providing canopy cover, shade, and moisture > Reduce energy use for cooling > Reduce extreme heat by providing canopy cover: increase shade, move heat through transpiration, and reduce energy use for cooling > Improve air and water quality from trees and vegetation > Become thermal refuges for urban dwellers |
| Fewer days with extreme cold | > Shifts to milder hardiness zones and altered plant habitat suitability > Reduced mortality of diseases and pests caused by extreme cold | > Reduced demand for energy to heat homes > Potentially fewer deaths from extreme cold > Increased survivability in disease-transmitting insects | > Strategically placed trees further reduce wind and improve passive solar, thus reducing energy use > Improve conditions for physical activity |
| Altered precipitation creating wetter conditions in some seasons | > Wet conditions may favor some plant pathogens | > Increased mold exposure leading to upper respiratory symptoms > Shifts in water quality and quantity | > Enhance filtration of pollutants and improve water quality > Canopy interception of precipitation and buffering rain cycles |
| More frequent heavy precipitation events | > Increased stormwater runoff and localized flooding > Mortality of trees in flood-prone areas > Soil saturation and slope failures | > Disaster-related injury and death > Reduced water quality > Mold and property damage > Disruption to food systems | > Reduce runoff from forest interception and absorption of rain > Root systems prevent erosion and property damage |
| Elevated risk of drought or aridification | > Mortality of drought-susceptible trees > Reduced forest growth and health > Increased stress on forests and shifts to non-forest vegetation | > Reduced water supply > Disruption to food systems > Increased fire risk > Increased dust, smoke, and fine particulates in air | > Enhance moisture retention in landscapes helps buffer shifts in precipitation > Improve water quality and storage by healthy soils > Interception and filtering of particulates |
| Increases in carbon dioxide (CO2), a greenhouse gas | > Increased pollen production | > More allergens > Increased respiratory illness and asthma > Human physiology stressor | > Reduce impacts from selection of lower-allergen or female trees > Reduce localized CO2 levels |
Rising temperatures and more frequent heat waves can lead to heat-related illness and mortality, reduced air quality and increased levels of particulates and allergens that contribute to cardiovascular and respiratory illnesses. Extreme weather sets up conditions for increased flooding and storm events, and more frequent and intense wildfires. Sea level rise introduces risks for coastal properties. These localized events and changes can directly impact basic life support, such as loss of homes or water contamination, and can introduce indirect health effects, such as psychological trauma and grieving. Visit the CDC’s Climate and Health Program and the Center for Climate Change and Health for more information on how climate change affects human health.
Urban forest ecosystems are also affected by a changing climate, and damage to urban forests can degrade the benefits that these ecosystems provide to human communities. Urban forests are vulnerable to rising temperatures and altered precipitation regimes, which can increase plant stress and affect which tree species are suitable in a particular area. Altered conditions also increase threats from forest pests and invasive plant species. Extreme storms can lead to stormwater overflows and flooding, particularly in areas with high levels of impervious cover, as well as downed trees and other disturbances. Visit the National Climate Assessment for more information.
Understanding how climate change will impact your region in general and your community in particular is a critical step in effectively addressing climate and human health impacts.
Individual cities are exposed to different climate stressors based on regional climate changes as well as local geographic conditions. For example, the coastal city of Providence, Rhode Island is susceptible to sea-level rise and severe weather related to hurricanes and coastal storms, such as high wind, flooding, and coastal erosion. Specific site-level conditions within a city also matter—in Providence, low-lying coastal areas and floodplains are at greater risk of coastal storms and flooding while forests in upland settings are more susceptible to high temperatures and drought.