Sixteen thousand people died in Europe during the summer of 2022 simply because it was too hot. Last summer in the US, when older people fell down on tar during heat waves, they had to be treated first for burns. Scientists believe that July 2023 was the hottest month on record. Last year, we read of multiple disasters worldwide: extreme heat waves in the USA, various parts of Europe and Asia; over 4,000 wildfires which raged in Canada, as well as a devastating one in Hawaii; and severe monsoons which caused extreme floods in many parts of Asia.

All of the above are attributed to global warming and climate change. Our actions that emit greenhouse gases have increased the Earth’s temperature faster since 1970, than any other period in the last 2000 years. This global warming has wrought havoc on the Earth’s climate – such as warming oceans and resulting cascading impacts such as melting icebergs, sea level rise, coastal flooding, and saltwater going up rivers, all of which disrupt livelihoods, food and water security.

The most challenging impact of global warming has been long-term shifts in the Earth’s weather patterns. There are more intense and frequent extreme weather events – such as storms, cyclones, floods and droughts, often leading to erosion and landslides. Erratic (out-of-season) rainfall, failure of monsoons and seasonal shifts have serious effects on agriculture, causing crop failure and therefore, affecting food security.

These effects of climate change are bad enough, but they are exacerbated by other human activities – namely, habitat loss and fragmentation, overexploitation, pollution, and introduction/spread of invasive alien species. For example, deforestation of catchment forests upstream results in erosion, and sometimes, slope instability, which, in turn, leads to landslides and downstream floods. There was a recent news item from the National Building Research Organisation that because of deforestation coupled with heavy rains, 1/5th of Sri Lanka is landslide-prone. Poor agriculture practices that leave soil exposed to heat when there is a drought, worsen its impacts. Relying on monocultures of crops when there are seasonal shifts (delayed monsoons, for example) can increase food insecurity.

Any process that emits CO2 is called a carbon source, and green plants that absorb carbon dioxide in the process of photosynthesis, are known as carbon sinks.

There are two ways of dealing with climate change. Human action/s to reduce emissions or to reduce carbon sources/enhance carbon sinks is called climate change mitigation. These actions include switching to clean energy, reducing the use of fossil fuels and increasing energy efficiency. However, even if, today, everyone, everywhere stopped all emissions of greenhouse gases, the temperature of the surface of the Earth would not cool for thousands of years to levels before the Industrial Revolution. Therefore, adjusting to observed or predicted climate change also becomes necessary. This is known as climate change adaptation. Adaptation could be as simple as growing drought-tolerant crops in the dry zone.

In December 2023, leaders of governments of the world met at the 28th Conference of Parties (COP). After contentious debates, negotiations and compromise, they agreed to ‘transition away from fossil fuels’. Some hailed this outcome as ‘the beginning of the end of fossil fuels’, others were deeply disappointed with the wording and that the proposed transition was not given a time frame.

Without waiting to see what will happen about shifting from fossil fuels at the global scale, what can we, the public, do?

Look to nature for solutions

Look, for example, at trees. Their leaves and canopies slow the rate of rainfall falling to the forest floor. Leaf litter functions like a gigantic sponge soaking the water up and slowing its release into the soil. This is a natural method of regulating floods and recharging groundwater. The roots of trees hold soils together. Without leaf litter and roots, rain falling on bare soil flows fast over the surface, resulting in erosion. Heavy rain falling on large areas of bare soil on slopes could cause landslides. Catchment forests reduce the risk of floods by increasing the amount of rainfall soaked into the soil, reducing and delaying the highest flows of floodwaters.

Meanwhile,  green plants serve as nature’s carbon sinks by removing carbon dioxide from the air during photosynthesis. During this process, they also replenish the oxygen that we breathe.

Nature has provided us with a ready-made solution for climate change adaptation. Why then, are we not looking to nature and using these solutions?

Nature-based Solutions (NbS) involve working with nature to address challenges of communities and societies, to provide benefits for both human well-being and biodiversity. This approach aims for a win-win both for us humans, as well as for biodiversity.

Compared to hard engineering solutions, NbS provide additional benefits called co-benefits as shown in the diagram above.

In contrast, the construction of a gabion retaining wall in a river or canal – for the prevention of erosion – may also provide clearer water but no other benefits.

The other difference is that NbS are cost-effective. In the mid-hills of Nepal, erosion and resultant landslides were common along many rural roadsides built without any safeguards to control erosion. A native plant – broom grass (Thysanolaena nees) – is a hardy perennial, with a network of roots that holds the soil together. When villagers planted broom grass along roadsides, this simple action significantly reduced erosion and landslides. An important co-benefit was that once this grass grew to about two metres, it could be cut and sold – as fodder for livestock, fuel and for brooms – which increased the household income of villagers. A standard cost-benefit analysis showed that over time, NbS were less expensive than hard engineering because there is far less maintenance necessary. But when the co-benefit of the income that communities earned was included, NbS were shown to be much cheaper than hard engineering solutions.

In the high Andes Mountains of Peru, livestock are grazed in high-elevation, wet, montane grasslands. There now are recurring droughts. With community participation, a pasture and water management plan was developed to ensure better management of water and establish a rotational grazing pattern (to avoid overgrazing). The ecosystem service of provision of year-round water was restored. Better management increased milk yield, fetching more income. The improved growth of grasses has also contributed to the conservation of threatened species – such as the vulnerable Andean condor (Vultur gryphus) and the Perúvian guemal (Hippocamelus antisensis) – another win-win for people and biodiversity.

Urban areas are most at risk from heat waves. They act as heat islands –  trapping the sun’s heat in concrete in buildings and the surfaces of roads. Green infrastructure (such as corridors of vegetation), green spaces (parks, grasslands and urban wooded areas), green walls and green roofs are extremely effective in reducing ambient heat. Increasing blue infrastructure (such as natural or artificial ponds and lakes) has the same effect. Barcelona, in Spain, increased tree coverage from 5% to 30% and reduced temperatures so much, that the city saved 10 million USD in annual bills for air conditioning.

Most cities have impermeable systems – such as tar, concrete, stone, brick, and roofing – that prevent water from filtering through the ground. The sponge city concept uses blue infrastructure to absorb rainwater, which is then naturally filtered by the soil to reach aquifers. Sponge cities are connected by open green spaces and waterways, which naturally retain and filter water. They also have green roofs that can retain and filter rainwater before releasing it into the ground. Also important in sponge cities are permeable roads and pavements, bio-swales (landscaped areas that collect stormwater runoff, filtering out pollution and letting the water soak into the ground) and bio-retention systems (depressed, landscaped areas for the discharge of stormwater). In a sponge city, in addition to providing natural flood control, co-benefits such as cooling, enhancing urban biodiversity and increasing recreation are also achieved.

In Sri Lanka, I think that we have long since forgotten to look to nature for solutions, in our unending quest for development, although traditionally, NbS were successfully implemented, using observation and common sense.

Colombo has the distinction of becoming the world’s first Ramsar Wetland City. It is in the floodplain of the left bank catchment of the Kelani Ganga and historically, was built on, around and interwoven with wetlands. However, now only about 2,000 ha of these wetlands – natural, giant sponges – remain. Some wetland parks, set up for the conservation of these critical soakage areas for the capital, are now being pruned and tamed as venues for wedding photographs. Sri Lanka had a ready-made sponge city……… but we have reclaimed it, dredged it, filled it and built infrastructure and roads, so that, often, with monsoonal rains, Colombo floods.

A recent article in the Sunday Times stated that 214 trees posing danger to people have been removed by the Colombo Municipal Council. Assuming that these are all old trees (about 30 years old), with trunks at least metre in a diameter, and that all plant species absorb an equal amount of carbon, these trees that were cut, stored about 4,639 tons of carbon.   We should have maintained and looked after those magnificent trees so that they did not pose a threat to people. Instead, these natural carbon sinks were grossly neglected, and we must now forgo the immense benefits they provide us.

We Sri Lankans must do better. Perhaps we must see green plants as tiny carbon-guzzling, oxygen-generating machines, just as we know that vehicles are petrol-consuming carbon-dioxide-releasing machines. What if each of us pledges to plant and look after a native herbaceous plant, a shrub or a tree, and tend it? Those who own estates or large gardens can plant trees, others with small gardens can plant shrubs, while those who live in apartments can grow plants in pots. Even if 1% of our population fulfils this pledge and plants trees and tends them, then we will have 221,810 more carbon sinks, absorbing an estimated 4,807,835 tons of carbon in their lifetime, absorbing the emissions for a year from one million cars.

As Jane Goodall says ‘What you do makes a difference, and you have to decide what kind of difference you want to make.’

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