That’s right: some of the world’s most important, life-saving medicines are derived from compounds found in plants, marine organisms, and microorganisms. More discoveries are made every year, but the bottom line? Many critical cancer treatments rely on access to healthy forests and other natural resources.

As of 2019, 118 of the top 150 prescription drugs sold in the US were derived from natural products. Home to about half of the total number of species on Earth, tropical rainforests are immensely important for modern and traditional medicine. So if anyone asks "why are rainforests important?" Here's one reason — and it's just scratching the surface!

When it rains, trees absorb stormwater via their roots—and intercept it on the surfaces of their leaves, branches, and trunks. Later, they release 95% of the water they absorb back into the air through the combined process of evapotranspiration, producing a powerful cooling effect. 

Trees and vegetation reduce surface and air temperatures through the process of evapotranspiration (a plant’s loss of water, mainly through the stomata of leaves), and by providing shade. Shaded surfaces, for example, may be 20–45°F (11–25°C) cooler at peak temperatures than unshaded materials are. Evapotranspiration, alone or in combination with shading, can help reduce peak summer temperatures by 2–9°F (1–5°C).

The total forest area is 4.06 billion hectares, and approximately 1/2 of that forest area is relatively intact. Around 1/3 of that is primary forest, or forests with no visible indications of human activities and ecological processes that are not significantly disturbed. 

It’s estimated that one hectare of Amazon rainforest contains around 900 tons of living plants.  

Nearly a third of that loss, 3.8 million hectares, occurred within humid tropical primary forest, areas of mature rainforest that are especially important for biodiversity and carbon storage.

Crucially, a majority of this carbon resides in forest soils, anchored by networks of symbiotic roots, fungi and microbes. Because of this, forests are typically considered carbon sinks (places that absorb more carbon than they release).

Through the process of photosynthesis, trees absorb carbon dioxide and water from the air and soil. Within their plant cells, solar energy and chemical reactions convert the water into oxygen and the carbon into glucose. The glucose is stored by the tree, while the oxygen is released back into the air.

Healthy forests encompass richly layered habitat types and provide shelter to a breathtaking range of biodiversity — including 80% of amphibian species, 75% of bird species, and 68% of mammal species.

There are an estimated 60,000 individual species of trees according to the world’s largest plant conservation organisation, U.K.-based Botanic Gardens Conservation International (BGCI). More than 11,000 of these are at risk of extinction, and 3,300 are critically endangered - meaning that without intervention, they will become extinct.

But forests are not equally distributed around the globe. More than 1/2 of the world’s forests are found in only 5 countries (the Russian Federation, Brazil, Canada, the United States of America and China) and 2/3 (66%) of forests are found in 10 countries.

Primary forests are forests that show no visible signs of human activities, and whose natural ecological processes have not been significantly disturbed. According to Global Forest Watch, they are "some of the densest, wildest and most ecologically significant forests on Earth."

Large-scale commercial agriculture (primarily cattle ranching and cultivation of soybeans and palm oil) accounted for 40% of tropical deforestation between 2000 and 2010, and local subsistence agriculture accounted for another 33%.

This is down from 16 million hectares per year in the 1990s. And while this is good news, we’re still losing forests at a blistering rate.

According to the US Department of Agriculture, Forest Service, "ecosystem services, otherwise known as nature's benefits, are the multitude of benefits that come from healthy natural systems." These include tangible benefits like food, fiber, fresh water, and climate regulation. They also cover the basic processes that underlie these benefits, including oxygen production, soil formation, habitat creation, and nutrient cycling.

The three most tree-rich families are Fabaceae, Rubiaceae and Myrtaceae.

This means that they only exist in one area. Endemic tree species are particularly threatened by deforestation, because if their specialist habitat is destroyed, they’re likely to become extinct. 

With enough oxygen to support humans and the other oxygen-dependent life forms we share the planet with.

These communities are most directly impacted when trees are cut down, but we all rely on the ecosystem services and forest products that the world’s forests provide.

Many of these people are women, and the time they must spend on basic subsistence is a major factor in the global gender gap. Around 252 million people living in forests and savannahs live on less than $1.25 a day; the natural resources around them are, literally, a lifeline.

That’s because indigenous peoples hold to their traditional ways of life and draw on ancestral knowledge to tread softly in the natural world. 

In a recent study, it was found that people are paying an estimated 8 billion visits a year to these areas — greater than the total global population. 

This is partially due to historically heavy settlement in Europe, and accompanying land-uses like logging and intensive agriculture. Europe also has less total land area. 

Tropical tree cover loss causes more emissions every year than 85 million cars would over their entire lifetime. 

According to the National Oceanic and Atmospheric Administration, about half of Earth’s oxygen comes from the ocean—mostly from oceanic plankton, which includes drifting plants, algae, and bacteria that can photosynthesize. One species of bacteria, the smallest photosynthetic organism on Earth, produces up to 20% of the oxygen in our entire biosphere. To put that in perspective, that’s more than all of the tropical rainforests on land combined.