Our trees are struggling. Triple‑digit heat places enormous stress on our urban forest, weakening tree health and accelerating canopy loss.
Why Heat Matters for Tree Canopy
High temperatures increase water loss, disrupt photosynthesis, damage roots, and make trees more vulnerable to pests and disease. Prolonged heat stress can weaken trees over time, making them more susceptible to drought, storms, and mortality.
With continued deforestation throughout Bexar County due to development, extreme weather, and drought, protecting our tree canopy is more important now than ever.
How Extreme Heat Impacts Trees
Water Loss & Leaf Damage
High temperatures increase evaporation from leaves, causing:
● excessive water loss
● leaf wilting
● scorching
● premature leaf drop
Severe or prolonged heat can lead to desiccation stress, especially when roots cannot supply enough water.
Photosynthesis Disruption
Extreme heat can damage chlorophyll, the pigment trees use to convert sunlight into energy.
This leads to:
● reduced photosynthetic activity
● slowed growth
● diminished overall health
Root System Stress
Heat affects the parts of the tree we can’t see.
High soil temperatures can:
● damage or kill roots
● reduce water absorption
● reduce nutrient uptake
Root stress compounds all other heat related problems.
Increased Pest & Disease Vulnerability
Heat stressed trees have weakened defenses.
Warm, dry conditions allow pests like bark beetles to thrive, increasing the risk of infestation and long‑term damage.
Growth & Reproduction Impacts
Extreme heat can cause:
● stunted or distorted growth
● reduced flower production
● lower seed or fruit yields
● disrupted timing of leaf emergence, flowering, and fruit ripening
These changes affect the entire ecosystem.
ALong Term Heat Stress Effects
Prolonged exposure to high temperatures can:
● weaken trees over time
● increase susceptibility to drought
● increase vulnerability to storms
● increase risk of disease
● lead to tree mortality
Heat stress is cumulative, and repeated events compound damage.
Why This Matters for Bexar County
Bexar County is already experiencing:
● continued deforestation due to development
● extreme weather events
● persistent drought
● rising temperatures
● shrinking canopy
Heat stress accelerates canopy decline, making it harder for trees to survive and recover.
Learn More & Take Action
To learn more about heat stress and how to protect your trees:
● Heat Stress in Urban Trees — PennState Extension
● Texas Forest Service – Tree Watering Tips
● SAWS Drought Restriction & Watering Rules
● Bexar County Water Control & Improvement District
We can all do our part to be responsible stewards of our environment.
Thank you for all you do!
