April 3, 2017

Climate Change, Water and Trees

The benefits of moving beyond our focus on energy.

When we talk about "energy", certainly in terms of policy, we usually mean what fuels our cars and heats our homes. Let's look at energy in a very basic sense, as in what happens when sunlight meets the ground. Say you have pavement, or land marked by degraded, exposed soil – the condition of much of the world's surface. When the sun beams down on that bare soil, solar energy is absorbed; it becomes sensible heat, or heat you can feel. Now amble over to a nice meadow, or well-managed rangeland with a thick carpet of grasses. Here solar energy touches down on plants that are transpiring. The solar heat is dispersed and becomes latent heat, embodied in water vapour, to be condensed and released as rain.

Climate is not a function of one sole metric; it is not a single story. And this is where we find opportunities.
When faced with an environmental predicament, it can be useful to inquire as to how nature has approached similar scenarios. For instance, in the case of wildfire, one can ask what processes used to keep that landscape hydrated and therefore resilient to fire. We learn that in the American west, beavers created wetlands and acted as "shock absorbers" that minimised fire risks. And when we ask what maintains our climate, the answer is water.
Were it not for the blanket of water vapour that buffers the Earth, our planet would be too cold to inhabit. The phase changes of water – from solid to liquid to gas, and back – represent an extraordinary transfer of heat. According to Australian microbiologist Walter Jehne, water-based processes in the atmosphere and the oceans, over land and across ice, govern some 95% of Earth's natural heat dynamics. It is the sheer immensity of water's role in climate that led scientists to conclude that humans could not have interfered with it. And yet, once we understand how water works – and how water intersects with factors we can influence, such as land use and plant cover – we can help to restore the processes that sustain the heat and energy balance, and therefore sustain our climate.
A deforested area in the middle of the Amazon jungle. Photograph: Raphael Alves/AFP/Getty Image
Peter Andrews, a farmer and author in Australia, made a statement that has stuck with me: "Plants manage water. And in managing water, they manage heat." Worth noting: we have de-vegetated a quarter of the planet – including destroying most of our natural forests.
Every square metre of Earth's surface receives an average of 342 watts of solar energy a day. Because of how humans have altered the environment, we now radiate back about 339 watts per square metre – a difference of less than 1%. If we managed our ecology better, how might we make up that three-watt differential? How about if we had a lot more plant cover and a lot less bare ground?

Post a Comment