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Tuesday, July 24, 2012

The Ecosystem Engineer

I’m currently fascinated by organisms that create conditions conducive to life for other organisms. Ecologists call them ‘keystone species,’ but I like the term 'ecosystem engineers.' These aren't creatures that are merely content to explore a little niche in their backyard. These are species that discover radically new ways of doing business, blow the roof off their ecosystem, and provide all kinds of opportunities that weren’t there before.
Often, this inventive organism will bloom into a flowering ‘radiation,’ expanding unchecked into new habitats and diversifying into multi-forked branches of exquisitely perfected species. Other species come along, using their ‘waste’ as a source of new creation.
Beaver Dam
Big as a Black Bear!
I imagine a pair of beavers damming a fast-moving river, providing deep, still waters to protect and raise their young. Their pond and wetland creations are used by many other species. Sediments and pollutants are removed from the waterway. Some trees are drowned, leaving skeletal deadwood homes and food for insects, spiders, birds, fungi, and plants. The beavers fell tall, broad-leaf trees, which regrow as bushy hedges, easily in reach of browsers. Near San Francisco, Alhambra Creek’s $10 million flood-improvement project was ‘destroyed’ by a pair of beavers who thought it needed additional improvement. Long-departed steel-head trout, mink, and otter returned to the creek. For the beaver, engineering waterways was a great strategy, lasting millions of years, as far back as the Eocene. There was even a giant beaver the size of a black bear. I would love to see it, but just two species remain with us today.

In the Pleistocene, another ecosystem engineer was at work. A huge variety of elephants, large, small, woolly, bald, even one with a spork, were instrumental in creating the savanna-grassland patchwork we see in parts of Africa, Asia, and the Americas. Uprooting trees, decimating forest edges, ancient elephants provided clearings for grassland to spread. Grazers benefitted, and so did our own ancestors. We also see elephants excavating dry riverbeds with their tusks, creating wallows essential to other species in the long dry season.
from Elephants: A Cultural and Natural History
Forest before Elephants
Forest After Elephants
Other ecosystem engineers include towering ancient fig trees, offering substrates and habitats for countless tropical epiphytes, insects and spiders, birds and primates, lichens, and various rainforest mammals. Coral reefs teem with life, generating a jaw-dropping richness of endless jewel-like diversity. 
Old fig tree with his friends, T. Woolley-Barker
         The soil below our feet positively seethes with ecosystem engineers. Our most productive terra firma was created by lichen, a fantastical chimera of fungus and algae, working together to harvest minerals from bare rock. Darwin himself devoted an entire book to the industrious earthworm. And how about the subterranean mycorrhizal network of fungus?  An incredibly dense network pushes and pulls nutrients, water, and other information beneath the soil, unseen, suppressing various insects and bacterial populations, nurturing specific trees, orchestrating evolutionary succession according to their own inscrutable plan, like a pulsing planetary neo-cortex. Who knows what they are up to…but you can bet they’re engineering their ecosystem in some pretty radical ways!

         And what about our atmosphere? Here’s where it gets really interesting. I recently visited a strange, salty, axolotl-filled volcanic lake in the mountains of Mexico. The shore was ringed with rounded, bleaching humps that looked for all the world like enormous decaying brain corals. It turns out these ‘stromatolites’ are the calcified byproducts of ancient photosynthetic bacteria that created our planet’s atmosphere 3.8 billion years ago. They are still at work today in a few isolated spots. Thanks to them, we have air to breathe, and a nice cushy ozone layer, which blocks out most of the UV light, allowing us (and many other species) to live on land. Their gift to us also transmits water vapor, burns up meteors, and keeps us warm. Thanks, stromatolites!
Alchichica Stromatolite Lake, T. Woolley-Barker
In each of these systems, a single, radical adaptation changes the world, making the whole much greater than the sum of its parts, and the ecosystem much richer than a random jumble of species. But what about humans? Surely we are the ecosystem engineer par excellence? We are rapidly changing the composition of the atmosphere, the temperature and weather patterns of the Earth, adding polymers that never before existed, bringing vast quantities of metals to the planet surface, cutting and burning forests, paving surfaces, and modifying every environment to suit ourselves. That’s our radical invention: we can figure out how to use ANY niche. 

But are we making conditions conducive to life? Sure, some future epoch will no doubt see the rise of complex plastic-eating bacterial communities, and some photosynthesizer will figure out what to do with all our carbon. And of course, the rats and cockroaches and pigeons and dogs and mosquitoes love us just the way we are. Aren’t we just another inventive organism, blooming into a flowering radiation, expanding unchecked into new habitats and diversifying into multi-forked branches of exquisitely perfected niche-exploiters?
I believe this is basically so. When humans encounter boundaries, we diversify into different jobs, and stratify into different classes. Propagules sail bravely off to find new worlds and new opportunities. But this time, its different. Barring a juicy planetary discovery and a quick way to get there, there’s nowhere left to go. Its time to figure out how to use this niche, Earth, in a way that will sustain us. That’s our radical invention, right? We can figure out how to use ANY niche. Which means figuring out a new strategy, a way to sustain a diverse web of life that we can be a part of. A way to change our waste into a resource for other organisms. A way to create conditions conducive to life, and discover radically new ways of doing business. A way to blow the roof off this ecosystem, providing all kinds of opportunities that weren’t there before.

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