Climate change and top predators!

President Obama just gave a speech outlining the real threat of climate change and what we can do about it, with a real plan! I encourage you to check out both the speech and plan outline, it is progress in the right direction that we desperately need.

While President Obama talked about American ingenuity and technology and such, I thought I’d write about the ecological side of things, unfortunately often ignored by political speeches. Perhaps ecology is not as exciting as solar panels or saving on gas, but there is a direct link between reducing CO2 emissions and things we can all agree are bad ass: top predators.

How do top predators regulate CO2 storage? Well, predators eat herbivores that eat plants that store CO2. If predators, such as wolves, are removed from a system, the prey population of deer explodes and those deer eat up much more plant material than they would if wolves were present. Thus, the plant community changes and degrades and holds a lot less CO2. When wolves are around, the deer population will not only be in check (i.e. less deer), but deer will also modify their behavior, such as by spending more time looking out for wolves and eating less plants. Thus, with wolves present, more plants grow into trees and store more CO2. There are many other factors that add to the positive effect of predators on climate change- check out Chris Wilmer’s work here.

Addition evidence comes from sea otters and kelp forests (also courtesy of Wilmers et al.). Sea otters are keystone species, or species that regulate ecosystem processes, in the lovely kelp forests we have here in Monterey Bay. Sea otters eat a lot of sea urchins, which, in turn, eat a lot of kelp. Sea otters are coming back from the brink of extinction after being hunted from the 1700s to the early 1900s, but they still only occupy around 65% of their former range. Where sea otters are present, urchins spend more time hiding and eating dead kelp material; with no otters around, urchins are free to roam the sea floor and graze kelp to near nothing. Kelp are like the trees of the ocean and uptake tons of CO2 from the atmosphere. In fact, the researchers estimated that on the carbon market, the services provided by sea otters in reducing CO2 are worth $200-400 million.

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Now, to bring this back to tiny predators, of course. People often ask me about why they should care about the Ohlone tiger beetle or predatory insects in general and I like to give many reasons, but one that I sometimes talk about (but, honestly, have not been 100% convinced of myself until now) is that of predatory insects ecological role as orchestrators of the rest of the food chain and ecosystem processes.

I now have evidence! A new study on spiders shows the importance of (mini)top predators in regulating CO2 storage and gives me confidence to tout this role on behalf of the Ohlone tiger beetle and tiny predatory creatures alike. What eats plants in the grassland? Herbivores, like Grasshoppers! And this new study shows that when spiders are around, grasshoppers eat a lot less grass and that grass grows faster and stores more carbon. Watch out wolves!- How’s that for an ecosystem service?

Two Ohlone tiger beetle females (note male mating with one) chomp down on a Buckeye butterfly caterpillar (Photo: Tara Cornelisse))

Two Ohlone tiger beetle females (note male mating with one) chomp down on a Buckeye butterfly caterpillar (Photo: Tara Cornelisse))

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About tcornelisse

taracornelisse.wordpress.com
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