The Quiet Work Trees Do for the Planet

When is a tree not a tree? We often think of urban trees as simply poles in the ground, islands unto themselves, but they are ecosystems all their own, swarming with vitality. Each sustains life, often in tiny forms: fungi, insects, and other small entities. However, trees’ abilities radiate out from there, and they are, in fact, protectors—and ones that are changing as our climate is changing.

Trees are many things in our climate-fragile world: shields, indicators, educators, and managers. Their work is largely unnoticed, so it helps to understand their quiet ways and their climate services if we are to help increase their numbers and their effectiveness. In fact, there are three types of trees, all well known to urban and suburban dwellers in different parts of the country, that are doing often unnoticed work but is proving essential to our own survival.

The blue-gum eucalyptus

The blue-gum eucalyptus (Eucalyptus globulus), for instance, adored for its beautiful scent and blue-hued leaves in neighborhoods across the American west, has also served as a windbreak, providing pockets of calm and a haven of cool, aromatic quietness. As our climate changes, more unpredictable weather arrives on our home turf: not just greater swings in temperature, but stronger and more frequent winds, as the jet stream’s usual pace is disrupted. The blue gum helps to ease these winds.

As a bonus, the tree is a conservation warrior, serving as an essential stopping-place for the endangered monarch butterfly (Danaus plexippus), a long-haul voyager that endures an annual trip of up to 2,500 miles from its breeding grounds in the U.S. and Canada, down to forests in central Mexico. The eucalyptus tree also plays a part in the evolutionary battle for survival by providing windbreaks from winter storms that affect the butterflies as they flutter by during their migrations. To survive, monarchs must have suitable microclimates, with trees having a range of sunlight from full sun to filtered light. These are services provided by exotic trees like the euc—not natives. Nearly all monarch overwintering groves in the western U.S. require non-native trees. This news is music to the ears of many California gardeners, who understand that while milkweed provides nourishment and habitat for the monarchs, their beloved eucalyptus offers safe haven. Monarchs rest in eucalyptus groves at about 75% of the state’s overwintering sites—necessary stopping points during a journey that grows more risky with each passing year. Keeping these plants in place will help neighborhoods and the wider world.

The bald cypress

The bald cypress (Taxodium distichum) is another urban climate warrior, but in different ways from the eucalpytus trees. Distributed primarily across the American south, the beautiful cypress is is often thought of as a swamp and wetland dweller. But it also thrives in drier settings. This high degree of adaptability to changes in soil and water content is another quiver in its armamentarium in the climate change battles. Flooding, for instance, isn’t a particular problem for the tree, even in normally-dry urban settings, because of its literal deep-rootedness in southern swamps. It’s the unsung hero of hydrology. Sea level rise along the coast also doesn’t bother the tree much because it’s become adapted to higher salinity. The cypress’ roots also thrive in compacted soil, its foliage and wood structure let it capture particulate matter, and its light, feathery needles make it easy to clean up after.

As a bonus, it’s also relatively disease-free, and sturdy during windy conditions. The Society for Municipal Arborists, in fact, named it Urban Tree of the Year in 2007 for its ability to thrive in urban environments. And let’s not overlook the tree’s seasonal beauty. So named because it drops its leaves in winter, the bald cypress turns a fiery orange as autumn approaches, working from green to tan and cinnamon, to shades of orange and red.

The olive tree

And finally, let us consider the ubiquitous olive tree (Olea europaea), whose fruit is an enduring source of delight at Thanksgiving for kids who cap their fingers with olives, for lovers of the olive’s oils, and to neighborhood arborists everywhere. In the United States, it grows widely, from California to Texas, Georgia, Florida, Oregon, Arizona, Alabama, and even Hawai’i. The olive tree doesn’t get big, reaching between 10 and 40 feet, but it’s recognizable in its numerous settings, both rural and urban. Odds are good that you’ve walked by one in a downtown area, with its lance-shaped leaves, dark green on one side and silvery on the other.

Olive trees are successful agents in the fight against climate change in part because of their sheer volume; there are nearly a billion olive trees growing today around the world. Most are in the Mediterranean region, but the millions of olive trees in the United States play a long game. With every passing year, they grow larger, and are able to sequester more carbon in tree biomass and soil. And they help to mitigate climate change not just by reducing greenhouse gases, but by easing erosion with their root systems, removing pollutants, and improving water quality.

All told, these three trees—and many others—in our cities stand as silent yet formidable guardians in the battle against climate change. They are not mere passive observers of our urban landscapes but active participants in the restoration of ecological balance. Through their leaves, they capture carbon dioxide, the very currency of global warming, and transmute it into the oxygen that fuels life. They’re nature's own alchemists, transforming the pollutants spewed out by our industrious ways.

In the shade of their branches, they offer respite from steadily increasing temperatures, countering the relentless urban heat island effect. Their roots, a complex network beneath our feet, help manage stormwater, reducing the burden on our overtaxed urban infrastructure. In our era of environmental uncertainty, urban trees are not merely a token of green in a gray world, but a testament to our commitment to a sustainable future, where harmony between human habitation and the natural world becomes more essential for our survival every day. In planting and nurturing them, we sow the seeds of hope for a healthier, more resilient world—where the fight against climate change is fought not just in international conferences and scientific laboratories, but in every leaf, branch, and root that graces our city streets.