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Best Available Science for Trees, Clean Water and Clean Air

Tree Science & Environmental Benefits

Scientific Tree Facts

Rainfall Interception Tree canopies intercept 10–36% of annual rainfall in urban areas, delaying runoff onset and reducing peak flow volumes during storms (Xiao & McPherson, 2016; USDA Forest Service, 2009). Reference : Xiao, Q., & McPherson, E. G. (2016). The role of trees in urban stormwater management . National Center for Biotechnology Information. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6134866/ Reference : USDA Forest Service. (2009). Trees for Stormwater Manage

BAS for Clean Air and Water

Trees, Water, and Health: An Evidence-Based Overview This article synthesizes current scientific evidence on how trees and forests contribute to water resource protection and human health. It is organized in three parts: (1) ecosystem services of trees for water protection, (2) links between tree-based water protection and health, and (3) implications and recommendations for research, policy and practice. 1. Trees Protecting Water: Ecosystem Services Trees and forest vegetati

Cooling Our Cities

How Trees Reduce Urban Heat and Protect Public Health Urban areas across the United States are heating up faster than surrounding rural regions due to the Urban Heat Island (UHI) effect , where pavement, buildings, and infrastructure absorb heat and radiate it back into the environment (EPA, 2023). As climate change intensifies, extreme heat has become a growing public health concern. Fortunately, decades of scientific evidence show that urban trees offer one of the most effe

Tree-Powered Health Benefits

Microplastics Health Risks

How Trees Help Protect Us from Microplastics and Related Health Risks Microplastics—tiny plastic particles smaller than 5 mm—are now found in the air we breathe, our drinking water, our food, and even inside the human body. Recent studies show microplastics in human lungs, blood, placentas, and arterial plaque , raising serious concerns about long-term health effects. While this issue can feel overwhelming, nature provides a powerful defense: trees . These living air filters

Pacific County Failing Seniors

Tree-Canopy Neglect Is a HEAL Act Equity Violation Washington’s senior population is facing a silent mental-health crisis—one that is unfolding not in hospitals, but in neighborhoods stripped of trees. As urban development spreads and canopy coverage declines, thousands of older adults are being left in hotter, harsher, and more isolating environments. This isn’t just an environmental setback; it is a public-health failure and, more importantly, a potential violation of state

Trees Protect Lungs

The Powerful Link Between Urban Greenery and Respiratory Health Respiratory illnesses—including asthma, chronic obstructive pulmonary disease (COPD), and respiratory infections—are on the rise in many communities, driven by air pollution, heat, and environmental stress. While public health solutions often focus on medicine and technology, a natural and highly effective intervention is frequently overlooked: trees . Extensive scientific research shows that urban trees are vita

Trees and Clean Air

Tree Science

How Trees Clean the Air We Breathe: What Science Shows Air pollution is a major public-health concern, contributing to asthma, heart disease, lung cancer, and premature death worldwide. While technology plays a role in reducing emissions, one of the most effective and natural solutions grows outside our windows: trees . Decades of research confirm that trees significantly improve air quality by removing pollutants, cooling the atmosphere, and reducing the formation of harmful

Schools Need More Trees

Protecting Children from Air Pollution Air pollution is one of the most serious environmental health threats facing children today. Traffic emissions, industrial pollutants, wildfire smoke, and airborne microplastics affect developing lungs and can lead to lifelong health problems. While schools cannot control every pollution source in their area, one powerful and low-cost solution is available right on campus: trees . Research shows that increasing tree canopy around schools

Cleaner Air

In Washington State, the importance of trees extends far beyond beauty and shade. Urban and community forests serve as a critical public health resource—removing harmful air pollutants, cooling neighborhoods, and protecting residents from respiratory illness. As wildfire smoke, traffic emissions, and climate-driven heat increase across the state, expanding tree canopy is one of Washington’s most effective strategies for protecting public health. 🌿 Trees Clean Washington’s Ai

Trees and Clean Water

Trees Protecting Fish

How Trees Protect Lakes, Rivers, and Fish from Pollution, Microplastics, and Algal Blooms Introduction Trees do far more than create beautiful landscapes—they are vital defenders of freshwater ecosystems. Along the edges of lakes, streams, and rivers, forests form living shields that keep water clean and aquatic life healthy. By filtering pollutants, stabilizing shorelines, and moderating water temperature, trees play a critical role in protecting not only the water itself bu

Trees Protect Well Water

Reducing E. coli and Filtering Pollutants Introduction Wells are vital drinking water sources worldwide, but their proximity to surface contamination makes them vulnerable to bacterial and chemical intrusion. E. coli—a key indicator of fecal contamination—and other pollutants pose considerable risks to well water safety. Increasingly, scientific research identifies trees and forested buffers as effective, nature-based solutions for protecting groundwater and, consequently, we

Urban Forestry Plans and Laws

Bellingham Urban Forestry

Executive Summary Bellingham Draft Urban Forest Plan (April 2024) The City of Bellingham Draft Urban Forest Plan (April 2024) establishes a framework that views trees as essential infrastructure for the city's ecological, social, and economic health. The plan is based on Washington State's Growth Management Act (RCW 36.70A.172), Shoreline Management Act (RCW 90.58), and Community and Urban Forest Act (RCW 76.15). It says that trees are tools for protecting waterways, fish a

Tacoma Urban Forestry

Executive Summary: Tacoma Urban Forest Manual 2025 Washington State Law: Combining Urban Forestry, Critical-Area Protection, and Public Benefit The City of Tacoma's 2025 Urban Forest Manual (UFM) is one of the most detailed municipal plans in Washington State for combining tree care, landscaping standards, and stormwater compliance. The Planning and Development Services and Environmental Services Departments of the City of Tacoma created the UFM. It ensures that the city comp

Vancouver Urban Forestry

Executive Summary Summary The City of Vancouver's Urban Forestry Work Plan for 2025–2026 sees trees as an essential part of public infrastructure, necessary for keeping the air and water clean, lowering the risk of flooding, boosting the local economy, and supporting the health and resilience of the community. Vancouver's plan shows how local governments can use Best Available Science (BAS) to protect critical areas, reduce pollution, and fairly increase tree canopy coverage.

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