Australia’s most catastrophic brush fire season ended a year ago, but not before it torched the country for nearly 80 days. Fires destroyed everything that could not escape from nearly 472,000 acres of burning forests and bushlands – the equivalent of nearly 270,000 football pitches (nearly 360,000 American football fields).

At one point, a television reporter stood on a hill overlooking a forest the fire has reduced to bare, charred trees. They were as naked as matchsticks sticking out of the ash-covered ground. The reporter held her microphone out toward the disaster so viewers could hear what she heard: a deafening silence where the cacophony of life had been just a day or two before.

By the time firefighters smothered the last blaze, 3 billion animals had been killed or displaced including reptiles, birds, amphibians, deer, wallabies, koalas, and kangaroos. Some species lived only in Australia; experts feared several were now extinct. As all victims of forest fires know too well, the damage doesn’t stop when the flames do. Sludge and ash killed thousands of native fish when they washed into New South Wales’ Macleay River. Thousands of people who survived the fire reportedly died later from the air pollution it caused.

Many other places in the world burned last year, too. Fires ravaged parts of southwest and northern China, Scotland, Poland, the Amazon rainforest in Brazil, Turkey, Ukraine, Syria; Tanzania and South Jersey, the Florida Panhandle, Colorado, and Arizona in the United States. Nearly 10,000 fires broke out in California, killing 31 people, destroying or damaging more than 10,000 buildings and reducing an area larger than the state of Rhode Island to ash. One fire consumed more than a million acres; officials declared it was California’s first “gigafire.”

Drought and heat produce the conditions for many fires. Insects play a role, too. Various species of beetles, some no larger than grains of rice, have chewed their way through tens of millions of pine-forest in North America. They took out 5 million nectars of forest in the western U.S. between 1997 and 2010. Once they were established, there was no way to fight them. The West had to wait until they are themselves out of food.

Drought and heat weakened the trees’ defenses, and warmer winters allowed the insects to hatch twice rather than once each year. From the Yukon to Mexico, pine trees turned from green to ghostly grey before falling like pickup sticks and becoming the ideal fuel for the next lightning strike or careless camper.

These disasters will keep getting worse because of the world’s unabated pollution from fossil fuels. The carbon dioxide we release when we burn coal, oil and natural gas is the principal human cause of climate change. Fire seasons are longer now in a quarter of the planet’s vegetated areas; in some places, the seasons are year-round.

In the old normal, fires were a natural and beneficial part of forest ecology. Pine cones evolved so the heat from fires melted the sap that held their woody scales closed. The scales opened and exposed seeds so forests could regenerate. Hellish fires often destroy the seeds now. Chainsaws have taken a huge toll, too. The world’s forests contained an estimated 3 trillion trees a few years ago, equal to about 422 per person. Agriculture and urbanization sacrifice about 15 billion trees each year while only 5 billion new trees appear. In other words, we have an annual tree deficit of 10 billion.

There are many reasons we should be concerned. The loss of biodiversity is one. About 80% of the planet’s species are forest-dwellers. Another is the loss of ecosystem services – the valuable benefits that trees provide us, humans, at no cost. Trees are one of nature’s busiest multi-taskers, sheltering birds and animals, filtering drinking water, replenishing ground water, removing pollution from the air, stabilizing soils, controlling floods, and beautifying cities.

They also save lives. More than half the world’s population lives in cities where temperatures average 10 oF hotter than surrounding areas. Climate change makes heat waves more deadly. They kill about 700 people in the United States each year, more than hurricanes, tornadoes, or floods. Urban trees shade and cool inner cities. As a bonus, they reduce the cost, fuel consumption and greenhouse gas pollution of cooling.

Trees provide much of the fruit we are told to eat. Nearly 30 varieties turn water, sunlight and the nutrients in soils into edible fruits including apples, cherries, peaches, pears, mangoes, coconuts, dates, nuts, and more. Only botanists and arborists are likely to think about this, but fruit is the host tree’s wombs, formed to protect the seeds that carry the genetic codes of their species.

Trees have been around for 385 million years, about 380 million years before the first humans, yet we are still learning things about them. Scientists recently found that trees are social beings. Those in the same vicinity talk to one another. They share nutrients and send out alerts when they are in distress, communicating through fungal networks. The German forester who discovered this calls it the “wood-wide web.”

While they are doing all these things, trees serve as critical links in at least two great planetary cycles. Water cycles through the biosphere, shape-shifting from liquid, to gas, to solid. It is a finite resource; there will never be more or less of it. Trees play their part by taking water from the soil and returning it to the air as a gas when it evaporates from their leaves. Carbon, which is necessary for all life, cycles through oceans, soils, plants, and animals, including us. Trees inhale it in the form of carbon dioxide (CO2) and exhale oxygen. We, humans, do the opposite: We exhale the CO2 that trees need; they reciprocate by exhaling the oxygen we need.

One function of trees is especially important right now. Like several other species and ecosystems, they are “carbon sinks”. They hold onto and store the CO2 they take in. This is beneficial because the Earth’s atmosphere is overloaded with CO2. During the last two centuries, industrializing nations emitted enormous amounts of it by burning coal, oil and natural gas. As science writer Peter Brannen observes in his recent must-read article in The Atlantic, we have already put more carbon into the atmosphere than the Earth has experienced in more than 3 million years. We are still adding 40 billion tons of CO2 to the atmosphere every year just by burning fossil fuels.

This excess carbon has profound implications for the planet and all of its species. For thousands of years, the Earth has kept the climate from becoming too hot by reflecting some of the sun’s energy back into space. But the excess CO2 from fossil fuels and several other “greenhouse gases” are blanketing the planet and preventing some of the heat from escaping. As a result, the average temperature of the Earth’s surface is rising (i.e., global warming) and that changes the climate. The result is deadlier storms, higher sea levels, unprecedented fires, prolonged droughts, record floods, and so on.

We have known this for decades, but we have done nothing about it. Now we are close to crossing the point of no return. If we want to avoid crossing that threshold, we must stop burning fossil fuels, take the excess CO2 out of the atmosphere, and bury it. Researchers are working on new technologies to do this, but trees already know how to do it without cost or unintended consequences. So, along with changing to zero-carbon energy, our immediate priority is to stop deforestation, reforest areas where trees have been destroyed, and create new woodlands where the land is suitable.

To be perfectly clear, trees are no panacea. We must restore and protect other natural carbon sinks, too, including soils, wetlands, grasslands, and oceans. Competing land uses, water availability, unsuitable soils, and climate can constrain forestation. Besides, it takes most trees a long time to reach maturity when they are most efficient at storing CO2.

Nevertheless, the first-ever study of trees’ carbon sequestration potential, published in Science magazine in 2019, concluded there is enough suitable land in the world to provide sufficient forest sequestration to erase 100 years of carbon emissions without affecting existing cities or agriculture. “If we act now, this could cut carbon dioxide in the atmosphere by up to 25 percent, to a level last seen almost a century ago,” according to researcher Tom Crowther, the senior author of the study. “Our study shows clearly that forest restoration is the best climate change solution available today.”

In another study, researchers found that an area the size of the United States could support sufficient trees to store two-thirds of the carbon human activity has released since the Industrial Revolution. More than half the reforestation potential is located in just six nations that have lost much of their forests. In descending order of potential, they are Russia, the United States, Canada, Australia, Brazil, and China.

Another shortcoming is that trees can’t hold CO2 forever. They release it when they burn, or die and decompose. That’s why the slashing and burning the Amazon rain forest must stop, as well as the destruction of rain forests in Indonesia to make palm-oil plantations. It’s why the National Forest Foundation launched a campaign in 2018 to plant 50 million trees; the Arbor Day Foundation intends to plant 100 million trees by 2022; the Nature Conservancy has a billion-tree program; and the World Economic Forum is sponsoring a campaign to grow, restore and conserve one trillion trees by 2030. And it’s one of the reasons that the famed biologist Edward O. Wilson, among others, says we should “re-wild” half of the planet.

But although carbon escapes as trees decompose, it happens slowly. It takes the needles of a Douglas fir 10 years to decompose. Roots decompose in 15 years, barks take 100 years, branches take 120 years, and the trunk of a tree two feet in diameter takes 500 years.

And according to the Sierra Club, one tree’s carbon uptake does not come close to one human’s carbon output. A tree may sequester about 400 pounds of carbon dioxide over 25 years, but the average American emits the equivalent of about 20 tons a year.

So, global warming is a problem that requires several simultaneous solutions and international scientist tell us there is less than a decade left to do them. They include ecosystem restorations and the recapture of atmospheric carbon. But most of all, we must stop dumping carbon dioxide into the Earth’s atmosphere. If we don’t, all the trees in the world won’t solve the global warming problem.

World Tree Day

About 30 nations will observe Arbor Day this month. It will be a special day for a certain bristlecone pine tree in California. Named Methuselah, it turns 4,853 years old this year. It would be the oldest single living organism on the planet, except for an unnamed bristlecone pine nearby that scientists think has lived more than 5,000 years. It sprouted about the time that Egypt began building its pyramids.

But the bristlecones are adolescents compared to a grove of quaking aspens in Utah’s Fishlake National Forest. It consists of approximately 47,000 trees from a single root system. They are genetically identical clones in an organism that is thought to be 80,000 years old.

Yet for all the storms, fires, insects, and natural disasters they have survived over the millennia, even these ancients may not survive unmitigated global warming. We humans definitely would not because we have not evolved to withstand the conditions that unmitigated climate change would produce. It’s already happening to some ecosystems.

“A small population of our particular species of primate has, in only a few decades, unlocked a massive reservoir of old carbon slumbering in the Earth, gathering since the dawn of life, and set off on a global immolation of Earth’s history to power the modern world,” Peter Brannen writes. “As a result, up to half of the tropical coral reefs on Earth have died, 10 trillion tons of ice have melted, the ocean has grown 30 percent more acidic, and global temperatures have spiked.”

So, people and their leaders around the world must overcome the influence of the fossil energy industries, the inertia of the carbon economy, the fear of change, the denial of crisis, and the propaganda that global warming is a hoax. We have a lot to do in a very short time.

Still, take a moment to hug a tree on Arbor Day. Hug several. Then plant some. They are one of nature’s most remarkable gifts. And if we save them, they will help save us.