From heatwaves to rising seas: How trees defend us

It is common knowledge that planting trees tackles the causes of climate change by absorbing carbon emissions. Less known is the fact that forests also treat the symptoms of climate change, whether they are heatwaves, drought or crumbling coastal towns.

Here’s how. The outsize potential of trees to halt the climate crisis has generated a lot of media buzz recently, and rightly so – trees have an enormous capacity to absorb carbon emissions. Yet something crucial is missing from these stories. Forests don’t just absorb carbon; they also defend us from its most devastating impacts.

Heatwaves have been scorching India and Europe this summer, killing dozens of people. This July was the hottest month ever recorded, while the previous month was the hottest June on record. But as our air-conditioning systems whirr incessantly, providing much-needed respite from the stifling heat, they guzzle masses of fossil fuels, which in turn heats the planet. Our houses may stay cool, but the planet doesn’t.

There’s a growing recognition that one of the best technologies for tackling overheating cities was invented long before humans appeared: trees. Bringing parks, green spaces and canopies into cities has a cooling benefit during hot days; plants absorb water and then release it through evaporation, in the same way sweating keeps us cool.

On a sunny day, from evaporation alone, a single healthy tree can have the cooling power of more than 10 air-conditioning units. That’s not including the shade they provide for buildings, which in the United States can reduce air-conditioning costs of detached houses by 20 per cent to 30 per cent. And instead of emitting more carbon, trees absorb it. Not to mention, trees have the ability to filter air pollution, improving our health and that of the planet.

The city of Melbourne, Australia, is aiming to almost double canopy cover – from 22 per cent to 40 per cent – by 2040 to tackle heatwaves. Around 3,000 new trees will be planted each year.

This way of using nature to adapt to climate change, known as “ecosystem-based adaptation” or “nature-based solutions”, is, quite literally, a breath of fresh air.

It’s part of a much larger paradigm of environmental problem-solving called nature-based solutions. The United Nations Secretary-General’s Climate Action Summit this month will provide an opportune moment to catapult nature-based solutions to the forefront of climate action.

Moving from cities to coasts, forests are again a major defence against extreme weather.

One of the more ominous prospects of climate breakdown is rising seas that threaten to sink cities or slowly drag them into the ocean. The evidence is overwhelming that mangrove forests are effective and cheap natural barriers against coastal floods and shoreline erosion. They reduce both wave height and wave force. In fact, if all of today’s mangroves were lost, the global damage from flooding would be an extra US$82 billion (S$113 billion) a year.

We do not protect the forests; the forests protect us.

Drought is another worldwide crisis – already here for many, looming ominously for others. Even as early as 2025, half the world’s population will be living in “water-stressed areas”. When we fell trees, the problem deepens because roots act like sponges that absorb rain and recharge groundwater supplies. Without them, water flushes straight through the soil and isn’t stored for times of need.

It’s this realization that led to the ambitious “Great Green Wall” in Africa. The Sahara Desert has expanded by 10 per cent since 1920, eliminating grazing land and waterholes in its way, and imposing financial ruin for nearby villages.

To halt the process of desertification, 21 African countries are collaborating to restore an “8,000km natural wonder” of trees and shrubs across the width of Africa to lock in soil moisture and to keep the lands productive. The UN Convention to Combat Desertification says the endeavour can create 10 million green jobs by 2030.

This month in India, the convention is bringing 197 countries together to explore how these types of restoration efforts can thwart desertification. The Global Adaptation Commission, of which I am a member, seeks to accelerate adaptation action and increase political support for building climate resilience. A new report by the commission is making a pitch for scaled-up investment in nature-based solutions for climate adaptation.

Heatwaves, droughts and coastal storms are just three examples in which forests defend us from extreme weather, but there are far more. Carefully planted tree species can act as firebreaks, keeping trees next to farmland can protect crops from the erosive forces of intense rain, and forests can alleviate inland floods due to the sponge-like way they absorb water.

The latest UN Intergovernmental Panel on Climate Change report on land and climate change notes that land surface air temperature has risen nearly twice as much as the global average. Forests therefore play a critical role on the front lines of our efforts to guarantee resilience in a climate changing world.

Using ecosystems and nature-based solutions to adapt to climate change means we’re keeping biodiversity safe. The zero sum between development and environment vanishes. This is not nature or people; this is nature for people.
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