Nature disturbs

A few posts ago, I talked about how humans disturb nature. I might have made it look like disturbance is a typical human thing, and mostly bad for nature. Yet nothing is further from the truth.

Disturbance is extremely natural, and even vital for biodiversity. It has been around for as long as the earth.

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Disturbance is a vital part of the circle of life, and one of the main gears that keep it going.

A few days ago, for example, a minor storm passed over Belgium. Nothing bad, nothing out of the ordinary, yet there was some decent damage. A few old trees fell down, a few branches got ripped off. Minor damage, but this kind of damage might play a big role in driving diversity.

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A minor storm, force 6, ripped off branches and threw over some old trees

There is an interesting correlation between diversity and levels of disturbance: an undisturbed system is in climax, a few species will overshadow everything, those with the highest competitive power will be dominant. They won’t leave much room for other species underneath them. Like an old beech forest, for example, with virtually nothing growing on the forest floor.

Yet a few minor disturbance events like this little storm can create an interesting dynamic. A few small gaps, light penetrating through the canopy, opportunities for species in the understory. These opportunities help diversity to improve.

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Yet if disturbance starts to get too intense, or these disturbing events start to follow each other too fast in time, opportunities become reduced again. Before you know it, before you have time to grow to full maturity, you get struck by a new disturbing event, and die again. Only those that can handle these extreme stress-levels will be able to thrive. Diversity inevitably goes down again.

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It is thus at intermediate disturbance levels that diversity is at its highest. It has been like that forever, and there is nothing unusual about it. Yet there is indeed something out of the ordinary to these anthropogenic disturbances: they change the disturbance regime, and thus the system to which nature has been adjusting.

And the results of that are highly unpredictable.

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