Understand Why Trees Matter

Learning Objectives 

After completing this unit, you’ll be able to:

  • Understand how trees play a key role in addressing climate change.
  • Describe the ways trees benefit human health and equality.


Climate change isn’t a distant threat. Our planet is changing dramatically and quickly—and according to the National Aeronautics and Space Administration (NASA), human activity is the main driver. 

Today’s climate emergency stems from the buildup of greenhouse gases, mainly carbon dioxide (CO2), in the atmosphere. These gases trap heat, raising global temperatures. The climate science community stresses that without significant progress in reducing greenhouse gas emissions, global temperatures could rise above 1.5° Celsius within a few decades.

It’s critical that we take bold steps now because even 0.5° Celsius can make a big difference.

The risks to our world would dramatically increase if global warming reaches 2° Celsius compared to 1.5°. For example: 

  • 10 times more ice-free summers in the Arctic Ocean every century
  • 60 million more urban residents exposed to severe drought by 2100
  • 1.7 million more people exposed to severe heat waves every 5 years

Illustration of the projected risks to the planet associated with 2° versus 1.5° Celsius increase in global temperatures. 

We’re already experiencing the hottest decade on record. Glaciers and ice are melting at alarming rates, oceans are warming faster, and apocalyptic fires are raging from the Amazon to Australia. Our health, food and water supply, and economic growth are at risk. Climate change disproportionately affects the most disadvantaged and vulnerable populations, exacerbating existing economic and racial inequalities.


You can learn more about climate change by completing the Create a Sustainable Future trail and checking out Project Drawdown.

There is no one solution for combating climate change. We need a portfolio of actions that reduce emissions from sources like fossil fuels, and protect and enhance carbon sinks, which remove carbon from the atmosphere.

Enter forests, the best tool we have for removing carbon from the atmosphere, and a critical part of sustainable development.

Forests, Climate Change, and Sustainable Development 

Probably the most well-known benefit of trees is their power to act as a carbon sink by absorbing carbon dioxide (CO2) from the atmosphere. During the process of photosynthesis, trees use the energy of sunlight and take CO2 from the air and water from the ground. As they convert this energy into wood, they release oxygen into the air. In addition, trees help the soil around them to capture even more CO2 as limbs and other woody debris fall and break down. Here are a few facts about the hard work that trees do:

Trees provide additional benefits every day. They offer cooling shade, block cold winter winds, improve biodiversity, purify our air, prevent soil erosion, clean our water, and add grace and beauty to our homes and communities. Fun fact: 80% of known plants and animal species inhabit forests, with tropical forests alone hosting over half of the world’s biodiversity. 

Without forests, life as we know it would cease to exist—forests are intimately entwined with the world’s human and environmental systems. However, since the dawn of human civilization, nearly half the world’s forests have been cleared or degraded, largely to feed our growing population. Today, of the approximately 6 trillion trees that once covered half the earth’s landmass, only 3 trillion remain, and we’re still losing 15 billion every year. 

With deforestation continuing at an alarming rate, the health of remaining forests is declining rapidly with a high rate of forest biodiversity loss. The UN’s Report on Biodiversity estimates that as many as 1 million plant and animal species are currently threatened by extinction—that’s nearly 11.5% of the estimated 8.7 million global species. The number-one cause of species loss is land-use change and deforestation, the second is direct exploitation of species, and the third (and fastest growing impact) is climate change.

A quote from Salesforce CEO and founder Marc Benioff on the urgency of climate action over an illustration of a forest: “This is a time of action, not words. We are at that point of urgency with our planet.”

So, What If We Could Reverse Forest Loss? 

It’s estimated that nature-based solutions, such as reforestation, could provide up to one-third of the cost-effective climate solutions by 2030 needed to meet the 1.5° Celsius goal.

These solutions can also provide massive human health, economic, and biodiversity benefits:

  • Forests contribute to the health and well-being of people. In the US alone, trees absorb 17.4 million tons of air pollutants, preventing 670,000 cases of asthma and other acute respiratory symptoms annually.
  • Forests in and along coastal ecosystems, such as mangroves, provide nurseries for marine life, and help store carbon that would otherwise contribute to ocean acidification.
  • Risks from extreme weather events, like landslides and floods, are diminished by forests. 
  • By one estimate, restoring 350 million hectares of degraded and deforested lands around the world would create up to $9 trillion (USD) in net benefits. Many would accrue to poor rural communities, helping alleviate poverty. The wider benefits include social and environmental gains in water and food security, biodiversity conservation, and climate protection that help us all. 
  • Restoring healthy forests creates jobs. 
  • A recent WEF report revealed that sustainable management of forests globally would create $230 billion in business opportunities and 16 million jobs worldwide by 2030.

  • Trees filter precipitation to purify ground and surface water. The Amazonian rainforest keeps the air humid for over 3,000 km inland and transpires twenty billion tons of water daily. If its rainforest is lost, the Amazon would become a desert.

All these benefits add up, making it clear we need to significantly invest in trees. Realizing the potential of nature-based solutions like forests won’t be easy. If you plant a new tree every second, it would take around 11 days to plant 1 million trees. For 1 billion trees, you would need 31 years. Planting 1 trillion trees would take 31,000 years—at one tree every second. While this will be challenging, there are solutions.

In the next unit, you learn how global organizations are joining forces to plant, restore, and conserve forests in the context of a broader climate change response.