Water's role in climate change and natural disasters
Water's role in climate change and natural disasters
The complex systems dance of cause and effect
Cause and effect is often more complex than what might at first appear.
Because plants can be killed by insects, in order to help plants grow better, one may then think that one should apply pesticides to the soil.
However that is looking at the chain of cause and effect too simply. Pesticides killing insects which kill plants, is just one cause and effect chain in a network of influences in the soil. There are other important causal processes. Insects are cycling nutrients, maintaining soil structure, dispersing seeds, and pollinating plants. While adding pesticides may lead to short term increased yields, over time pesticides will degrade the soil, make it harder to grow plants, lead to less seed dispersal, and cause our food to become less nutritious.
This fundamental systems thinking error of cause and effect has affected a large sector of modern agricultural farming.
Wildfires are an example of a complex system. One way of dealing with fires it is to reduce the fuel load, by reducing the amount of trees and doing prescribed burns. That is one cause and effect chain. And its an important one. However there are also other wildfire cause and effect chains. Increasing the amount of trees can help rainwater infiltrate into the soil, which helps rivers keep running into dry season, and which helps increase groundwater. Leaving dead tree matter on the forest floor helps rainwater infiltrate into soil. Dead logs can hold 23 times the moisture of soil, and help keep a forest moist and humid. Tree roots can bring up the groundwater to hydrate the soil and vegetation during dry season. Trees evapotranspire water, that then blows inland to create more rain. Forests recycle evapotranspiration to create a more humid environment.
There are multiple cause and effect chains where increasing trees also helps with decreasing wildfire risk. To understand what actions we take in regards to trees and wildfires requires us to understand the whole system of cause and effects. The solution is more complex and context dependent than might seem at first glance. Most current fire management practices are focused only on the fire cycle and how to reduce fuel for fires, and have left out the water cycle in the equation. Increasing the water content in soils, air and ground will help reduce fires. So as an example if landowners protect trees, and build swales, check dams, and terraces on their property, which increase groundwater, soil hydration and year round creek flow, that can help reduce fire risk. An example where there is subtlety in the analysis, where one needs to look at the full range of cause and effects, is understanding when to leave dead plant matter on the forest floor to increase water levels, and when to get rid of dead plant matter on the forest floor to decrease fuel load. Its a more subtle calculation, that is context dependent, that involves weighing the benefits of increase water content with the problems of more fuel to burn. A scientific study of pine and mixed conifer forests in the Western USA showed that unmanaged forests where the debris is left on the forest floor, survive much better than managed forests where debris is cleared and the forest is thinned, because the unmanaged forests are more humid, and have moister soil [1]. Increased groundwater underneath unmanaged forests can also lower wildfire risk. (See Chad Hanson’s book “Smokescreen” for more discussion in regards to how management of forests and fire risks.)
In order to deal with the many issues of climate change, like drought, heat, fires, floods, hurricanes and extreme rains we have to understand the multiplicity of cause and effect chains of our earth system. Carbon emissions causing greenhouse effects causing global warming and extreme weather, is one cause and effect chain. It’s now a well known causal sequence. And an important one. But there are other important processes in the system also.
Here are water cycle cause and effect chains that play into climate change.
How well the landscape stores water in wet season for dry season helps determine impact of droughts and fires
How deep and what type of tree roots there are, along with how much groundwater there is, helps determine how landscape is hydrated into dry season
How well the landscape passes water inland from oceans through moisture hopping and how well it retains it through moisture recycling determines how much it rains, and the existence of droughts.
How well the landscape can increase humidity in the air through evapotranspiration affects how much fire risk is lowered.
How much evapotranspiration is happening from vegetation, soil and wetlands helps determine how hot, dry, and fast the wind, which helps determine amount of wildfire.
How well landscapes can undergo evaporative cooling helps determine how hot it is over land.
How well the landscape absorbs water, and how well the vegetation stops landslides, helps determine volume and velocity of floods
Land use affects the temperature gradient between land and sea, which helps determine frequency and amount of larger storms.
Soil quality, amount of forests and wetlands, and river overflow helps determine groundwater recharge
The earth is a complex systems with multiple cause and effect chains, and feedback loops. Understanding these will help us find solutions to droughts, heat, fire, floods, extreme weather.
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References:
[1] Bradley, Curtis M., Chad T. Hanson, and Dominick A. DellaSala. "Does increased forest protection correspond to higher fire severity in frequent‐fire forests of the western United States?." Ecosphere 7, no. 10 (2016): e0149
This a map of the regions studied in the paper.
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