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Adapting our country for change – part one: cooling

Updated: Oct 18, 2021

Even though I am a scientist, I find it easy to ignore how hard science is to do. I know, for example, that it took the physicist Isaac Newton years of work and isolation ― and a pretty unique mind ― to develop his theory of gravity. And yet I might have spent a total of a couple of days learning about gravity at school and university before moving on to the next subject. Needless to say, I am not a stunning physicist but all the work Newton spent going in the wrong direction, making mistakes, and having to figure things out is usefully ignored by our education system saving us much time and effort.

That's how science works: scientists spend years trying to understand something new, and once they do understand, they publish the knowledge so that everyone else can know it without the same effort. I know a person who worked on one article for decades before getting it published. This article was inevitably read by a select few other scientists (three? ten? As many as thirty?) interested in this particular area in a matter of minutes or hours.

Climate change is one of those areas of science where methods to address the problem are being actively developed. Great effort and great minds are invested in this field. But it seems many of the solutions proposed or in use to address climate change require action at a government level ― the individual can buy local food, cut down on car trips and overseas travel, or buy green energy if they are interested in making their own contribution to reducing greenhouse gases. However, these activities will not change the local climate on their own. That requires mass action as well as compulsion to act by governments using specific levers and drivers. If too few people act and / or the government fails to act, then individuals cannot alter the overall impact of greenhouse gas emissions.

Unless one takes a spiritual or ethical view ― that is reducing one's carbon footprint is the right thing to do by humanity and the planet ― it's hard to justify individual action in this way. But does this mean farmers and others in the environmental / agricultural sector need to wait for others to act? Is there nothing we can do to protect ourselves from the heat and drought predicted to worsen as a result of global climate change?

At Murrang Earth Sciences we are investigating this question. We want to develop a method or even a few methods by which others can actively cool their local environment. In so doing, we will identify ways people can mitigate the effects of climate change. So far there are promising leads as to what the ingredients to our recipe might be.

How do trees affect the climate? We want to find out! (Image: crop land in the Wimmera, Victoria)

Greenspace ― that is parks and gardens ― are well known to moderate temperatures in urban environments. While surfaces like roads and concrete drive temperatures higher in cities, both increased tree cover and increased tree density reduce temperatures. Within Shenyang, China, for example, temperatures in areas with proportionally high levels of concrete and asphalt can reach over 44°C while areas adjacent to rivers and parks are between 23 and 26°C. The cooling effect of greenspaces in urban environments does not happen at all times, with greenspaces in London cooling the surrounding area only 10 to 21% of nights in summer and autumn. Importantly, however, the nights where cooling was effective were the warmest nights.

A number of recent studies show that changes to land-use impact the climate of non-urban areas also. Studies of the impact of tree die-back in the Czech Republic found ground temperatures increased by up to 10°C when both trees and shrubs disappeared from landscapes in tree die-back areas. This was considered to be because the grasses which came to dominate these ecosystems in place of the trees cannot access deeper groundwater as trees can. It is this deeper groundwater which supplies moisture to cool the surrounding forest, with the grasses instead using the reserves of water in the soil much more quickly.

Snow cover was also found to last on average 11 days longer in forested areas in the Czech study compared to areas with die-back. In addition, temperature increases at specific points within the die-back affected areas were far greater compared to forested areas. Similar to the difference seen between greenspaces and impervious surfaces in cities (e.g. roads), temperatures of up to 60°C were measured in the dead Czech forest compared to 22°C within intact forests.

These studies show that the ways land is used and managed affects local climates, not just because of greenhouse gas emissions but because of the way different materials absorb and reflect heat. We know that trees cool landscapes sometimes by tens of degrees, by creating shade but also by pumping water into the surrounding atmosphere. Even if people "believe" climate change is driven by natural variability instead of greenhouse gases, trees offer a method by which people can cool their farms and gardens whatever the drivers.

If we can use trees to cool, how would this be done? How much land would be needed to change the local temperature? What type of vegetation would be best? Or what kind of change in land use might be required? This is something we are working on, that we are turning into answers, and we want to make available to you all to use!

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