Planning for Trees Improves Climate Resiliency
As the climate changes and the earth warms, extreme heat days (temperatures over 95°F) have increased in frequency and wildfires fueled by dry vegetation burn bigger and for longer, negatively impacting air quality both locally and nationally. While unable to completely cancel out the impacts of an extreme heat day or very poor air quality due to fire, tree planning to create a robust urban forest can cool a community to bearable temperatures and improve air quality in the long term, which provides a baseline of protection when more extreme events occur.
One way that trees help cool cities is by reducing the urban heat island effect. You’ve likely experienced the relief of taking shelter in a shaded area on a hot day or felt the difference between going for a walk through a wooded forest versus on a shrubby hillside. The shade is cooler because shaded areas absorb and retain less heat, and the wooded forest feels cooler than the shrubby hillside, even on a day where the actual temperature is the same in both places, because the tree’s canopy absorbs some of the sun’s heat before it ever reaches the ground. In fact, air temperature can be as much as 10F cooler in shaded areas and the surface temperature can be 20–45°F cooler than in unshaded areas!
And it’s not only daytime temperatures that are affected by a lack of trees. All those dark, urban surfaces like roads, and buildings, retain the heat they absorb throughout the day and release that heat in the evening, increasing nighttime temperatures as well.
The other benefit trees provide in cities is by improving air quality. We’ve all heard that trees absorb carbon dioxide, which is a vital role to play in cities where car traffic is at it’s worst. In places with ample tree canopy, the urban forest absorbs some auto emissions, improving air quality. But without trees, those emissions are not absorbed. Not only does air quality worsen, but the emissions create ozone, which traps even more heat, exacerbating the temperature issue.
Sweltering days and poor air quality prevent a city’s residents from getting outside or, when going outside can’t be avoided, the risk of adverse health events, like asthma attacks and heat stroke increase. While some cities and neighborhoods have a robust urban forest and are amply shaded, there are significant discrepancies in canopy cover between the richest neighborhoods and the poorest. Planning for trees can help correct those discrepancies.
Urban Forestry as Environmental Justice in Action
Lower tree canopy cover is often correlated with lower-income neighborhoods and communities of color—areas that have historically been disproportionately impacted by climate change. As such, these disadvantaged communities are more vulnerable to pollution hazards, extreme heat, and the health issues that result from long-term exposure to these conditions. At its core, climate resiliency is an issue of equity and environmental justice, and the benefits that trees provide are real and quantifiable.
Happier, healthier, less stressed residents are certainly an economic benefit, but even the trees themselves provide ecological services that generate a return on the investment a city makes toward growing a healthy and robust tree canopy. Unlike built infrastructure and equipment whose value depreciates over time, a tree’s value increases as it ages. Older trees are larger, creating more canopy cover, which increases shade and the amount of CO2 the tree can absorb. Additionally, older trees have more established roots, which fortify the tree and make it more drought resistant—another vital role trees play, as climate change decreases annual rainfall. As such, trees should be treated as infrastructure and planned for with equal importance as sewer lines, streetlights, and sidewalks. Like other infrastructure, trees must be included in the beginning of the planning and design phases, so they have the space to grow without creating conflict with components of infrastructure and to ensure a plan for their long-term maintenance.
Two Methods to Planning for Trees
Planning for trees requires thoughtful consideration of numerous issues by multiple entities. Two processes can form the basis of good tree planning, and these include urban forest management planning (taken on by cities and municipalities) and Green Neighborhood certification (pursued by private developers).
Urban Forest Management Planning
The goal of an urban forest management plan (UFMP) is to create a sustainable urban forest that optimizes tree benefits while meeting established safety and economic goals. Dudek has worked with several cities throughout California, including San Jose, Pasadena, and Los Angeles on developing long-term urban forest management plans (UFMP) that provide the steps toward achieving an optimal level of canopy cover. In each instance, the following steps are required:
- Assemble the right team of experts and stakeholders
- Analyze the current condition
- Engage the community
- Create the plan
- Implement your living document
A UFMP must be informed by research, data, and urban forestry best management practices, as well as the collective vision of city staff, elected officials, residents, and stakeholders. The UFMP process develops a strategic plan that is based on the values of the city and its stakeholders (especially the residents and community), clear action items, and an implementation plan. A successful UFMP sets a clear path for adapting a city’s trees to climate change and creating a resilient community.
See how we helped the City of Los Angeles undertake the first steps toward crafting an urban forest management plan, engaging more than 40 stakeholder organizations and city departments.
Green Neighborhood Certification
The Green Neighborhood Certification was created by the Sacramento Tree Foundation to give developers a framework for developing equitable, healthy, sustainable, cost-effective canopy cover in neighborhoods. This voluntary effort signals to homebuyers that consideration has been paid toward resale value and energy efficiency of their home, as well as simple enjoyment of their neighborhood. The Sacramento Tree Foundation outlines the steps toward certification as follows:
- Develop a plan for canopy cover.
- Consider existing trees.
- Strategically select trees
- Place trees intentionally
- Outline a plan for long-term tree care
- Install trees effectively
Climate change is here, and communities are already dealing with the impacts from increased heat, extended periods of drought, and wildfires. Whether our cities are resilient and livable in the future will in part depend on trees and the multiple environmental services and public health benefits they provide. Trees take time to grow, so whether you’re a city facing the reality of low/declining canopy cover or a developer wanting to make your project more desirable, the time to act is now to have create a robust urban forest with tree canopy cover that will help sustain healthy communities in the decades to come.
For more information on urban forest management planning, contact Dudek Urban Forester, Ryan Allen.