Planting billions of trees across the world is one of the biggest and cheapest ways of taking CO2 out of the atmosphere to tackle the climate crisis. But even having one tree has environmental benefits.

For decades, it’s been clear that the Earth’s climate is changing, and it’s almost universally agreed that humans have had a role in it. The hard science shows that carbon dioxide (CO2)—the primary greenhouse gas emitted through human activities—is the main driver of climate change, although other greenhouse gases and air pollutants also affect the climate. However, while these facts are dire, we still have the potential to determine the future course of our climate.

There’s a simple, nature-based solution to climate change: planting trees.

Even one will make a difference.


Around the world, many islands are slowly but surely being submerged. Rising sea levels could very well cause several islands to completely disappear before the 21st century is over.

First, the facts: climate change is intensifying, and its effects will be felt everywhere

In August 2021, the Intergovernmental Panel on Climate Change (IPCC)—the United Nations body for assessing the science related to climate change—stated in its Sixth Assessment Report (AR6) that changes in the Earth’s climate have been observed in every region and across the whole climate system. Many of those changes are unprecedented in thousands, if not hundreds of thousands of years; and some of the changes already set in motion—such as continued sea level rise—are irreversible for, perhaps, hundreds to thousands of years.

However, the report goes on to say that strong and sustained reductions in emissions of CO2 and other greenhouse gases would limit climate change. While benefits for air quality would come quickly, it could take 20 to 30 years to see global temperatures stabilize, according to the IPCC Working Group I report, Climate Change 2021: the Physical Science Basis, which is the first installment of the AR6.

The Working Group I report addresses the most updated physical understanding of the climate system and climate change, bringing together the latest advances in climate science and combining multiple lines of evidence from global, paleoclimate and regional climate simulations; observations; and process understanding. It shows how and why climate has changed to date, and how understanding of human influence on a wider range of climate characteristics, including extreme events, has improved.


Since the latter half of the 19th century, greenhouse gas emissions from human activities have been responsible for approximately 1.1 degrees Celsius of warming.

According to the Working Group I report, emissions of greenhouse gases from human activities are responsible for approximately 1.1 degrees Celsius of warming since 1850 to 1900; and it finds that averaged over the next 20 years, global temperature is expected to reach or exceed 1.5 degrees Celsius of warming. At that point, there will be increasing heat waves, longer warm seasons and shorter cold seasons. At 2 degrees Celsius of global warming, heat extremes would more often reach critical tolerance thresholds for agriculture and health.

Climate change is already affecting every region on Earth, in multiple ways. But what people experience in various places is often very different from the global average. For example, warming over land is greater than the global average, and it is more than twice as high in the Arctic.

The report projects that in the coming decades, climate changes will increase in all regions. But it is not just about temperature. For example:


Global warming increases the risk of drought. Water generally evaporates more quickly at higher temperatures. For that reason, hotter weather can result in drier soils.

• Climate change is intensifying the water cycle. This brings more intense rainfall and associated flooding, as well as more intense droughts in many regions.

• Climate change is influencing rainfall patterns. In high latitudes, precipitation is likely to increase, while it is projected to decrease over large parts of the subtropics. Changes to monsoon precipitation are expected, which will vary by region.

• Climate change is affecting the sea level. Coastal areas will see continued sea-level rise throughout the 21st century, contributing to more coastal erosion and more frequent and severe coastal flooding in low-lying areas. Extreme sea-level events that previously occurred once in 100 years could happen every year by the end of this century.


Spitsbergen is one of the fastest warming regions on Earth. Fourteen tidewater glaciers flow into the Hornsund Fjord—which nearly divides the island in half—and all of them have retreated substantially during the past three decades.

• Climate change is amplifying permafrost thawing. It’s also increasing the loss of seasonal snow cover, accelerating the melting of glaciers and ice sheets, and escalating the loss of summer Arctic sea ice.

• Climate change is altering oceans. Changes to the ocean—including acidification, more frequent marine heat waves, reduced oxygen levels and warming—have been clearly linked to human influence. These changes affect both ocean ecosystems and the people that rely on them, and they will continue at least throughout the rest of this century.

• Climate change is changing cities. For cities, some aspects of climate change may be multiplied, including heat (since urban areas are usually warmer than their surroundings); flooding; and, in coastal cities, sea-level rise.


Changes to the ocean due to a climate change—including acidification, reduced oxygen levels and warming—have been clearly linked to human influence. They affect both ocean ecosystems and the people that rely on them.

For the first time, the Sixth Assessment Report provides a more detailed, regional evaluation of climate change—including a focus on useful information that can provide advice on adaptation, risk assessment and other decision-making—and a new framework that helps translate physical changes in the climate, such as coastal flooding, droughts, heat and snowfall, into what they mean for society and ecosystems. This regional information can be explored in detail in the newly developed Interactive Atlas, as well as in the fact sheets, the technical summary and the underlying report.

The IPCC Working Group I authors hope that this assessment will be a reality check. For example, the report provides new estimates of the chances of crossing the global warming level of 1.5 degrees Celsius in the next decades; and it finds that unless there are immediate, large-scale and rapid reductions in greenhouse gas emissions, limiting warming to close to 1.5 degrees Celsius or even 2 degrees Celsius will be beyond reach.

Second, the good news: trees could save the climate

Meanwhile, researchers have identified mass tree-planting as a cheap and green way to lock carbon into the soil.


In our cities, some aspects of climate change will be exacerbated, including heat.

A Crowther Lab of ETH Zurich study, which was published in the journal Science in July 2019, shows that about 0.9 billion hectares of land worldwide would be suitable for reforestation. That could ultimately capture two-thirds of human-made CO2 emissions; and thus, it would be the most effective method to combat climate change.

The study showed for the first time where in the world new trees could grow and how much carbon they would store. The researchers calculated that under the current climate conditions, Earth’s land could support 4.4 billion hectares of continuous tree cover. That is 1.6 billion more than the currently existing 2.8 billion hectares. Of these 1.6 billion hectares, 0.9 billion hectares fulfill the criterion of not being used by humans. This means that there is currently an area the size of the U.S. available for tree restoration. Once mature, these new forests could store 205 billion tons of carbon: about two-thirds of the 300 billion tons of carbon that has been released into the atmosphere because of human activity since the Industrial Revolution.

The greatest potential for forest restoration can be found in just six countries: Russia (151 million hectares), the U.S. (103 million hectares), Canada (78.4 million hectares), Australia (58 million hectares), Brazil (49.7 million hectares) and China (40.2 million hectares).


In our cities, some aspects of climate change will be exacerbated, including heat.

A tool at https://www.crowtherlab.com/maps-2 enables users to look at any point on the globe and find out how many trees could grow there and how much carbon they would store. It also offers lists of forest restoration organizations.

The study authors say that while we all knew that restoring forests could play a part in tackling climate change, we didn’t really know how big the impact would be. This study clearly shows that forest restoration is the best climate change solution available today. But since new forests take decades to mature and achieve their full potential as a source of natural carbon storage, we would need to act quickly.

Third, the small efforts matter: tiny, urban forests have big value

The World Economic Forum states that tiny urban forests could be a secret weapon against climate change. They can be squeezed into school playgrounds or alongside roads. The method is the brainchild of Japanese botanist Akira Miyazaki, who realized his country’s woodlands were largely non-native. He set about planting 1,700 pocket forests throughout Asia.


In Europe, creating Miyawaki miniforests is becoming popular. Density is key.

Now the idea is catching on in Europe. The miniforests are created by planting native species very close together. They grow 10 times faster than conventional forests, generate 100 times more biodiversity and store 40 times more carbon. The Netherlands has planted 85 Miyawaki forests, while more than 40 have taken root in Belgium and France. Density is key, with a wide variety of native species required to recreate the layers of a local, natural forest. It’s also hoped these woodlands will form wildlife corridors and provide food for songbirds.

Fourth, the power of one: a single tree can make a difference

A study published in the science journal Environmental Research Letters on August 4, 2021, will make you ponder and appreciate the value of every, single tree.

In summer months, urban areas—with their fewer green spaces and higher amounts of impervious surfaces—get hotter compared to rural surroundings. This is known as the urban heat island effect.


Stand-alone—or “distributed trees”—can help to reduce evening heat in urban settings. They are especially important in areas where land for parks is scarce.

But according to scientists from American University, a single tree along a city street or in a backyard can provide measurable cooling benefits. “Distributed trees”—those that are stand-alone and scattered throughout urban neighborhoods—can help to reduce evening heat. As a result, planting even just one tree can be a cooling strategy, particularly in areas where land for parks is scarce.

To arrive at their findings, the researchers examined more than 70,000 air-temperature readings collected at multiple times across different locations in Washington, D.C., on one hot, summer day in 2018. The results showed that while urban parks provide important midday cooling, the key to cooling from individual trees happens in the evening. Cooling benefits from distributed trees were found to occur at around 6:00 or 7:00 p.m. and after sunset. Temperatures were 1.4 degrees Celsius cooler in the evening in neighborhoods where at least half the area was covered by canopy from distributed trees compared with areas that had few trees. Even in the predawn hour, areas with only modest distributed canopy cover (about 20 percent of the area) were cooler than those with no trees, showing that, on average, afternoon and evening cooling effects last well into the night.

In urban areas, people are more likely to live adjacent to distributed trees rather than parks. In D.C., there are many places to plant individual trees where canopy will shade paved or unpaved surfaces: on streets with single-family homes, on streets with row houses, in backyards or in small parks. This opens avenues for increasing the socioeconomic and racial equity of tree-planting.


The top five trees along the streets of Washington, D.C., include several species of elms, maples and oaks—all of which provide plentiful shade and cooling benefits.

This study confirms that planting individual trees should be considered as part of a strategy to combat rising temperatures in urban areas.

Fifth, read the trees: they could become your best friends

Trees have always been very special to me. Like many people, I like to count them among my friends.

Back in 1964, best-selling children’s book author and illustrator Shel Silverstein wrote a book about one of these amazing beings. It’s titled The Giving Tree.

How foresighted that title was.

Here’s to finding your true places and natural habitats,