Some tools are for the California water problem are man-made – and some come from Nature. In NewScientist (22 October 2016, paywall) MacGregor Campbell reports on using Nature’s engineers to solve the complex problems of water in California – beavers:
In 2010, local landowner Betsy Stapleton got in touch with [NOAA researcher Michael] Pollock after reading about some of his research. Pollock was interested in something called beaver dam analogues. Typically consisting of a line of posts set across a stream bed and interwoven with willow and cottonwood branches, these faux dams slow water down and widen out a stream to form a pond. The goal? To attract beavers. Putting one up is like prepping beaver real estate for sale.
In Sugar Creek, much to Stapleton’s delight, the faux dams worked. As she wades through soft muck into surprisingly pristine pond water, she points out evidence of beavers all around. Sticks with chew marks are strewn across the pond bottom. A scent-mound of dried mud stands guard telling interlopers that the pond is spoken for. Vegetation has been stuffed into both dam analogues. “They like to plug every little hole,” says Stapleton.
Of course, there are no guarantees.
[Jimmy Taylor, a wildlife biologist with the US Department of Agriculture] and his students recently trapped and relocated 38 nuisance beavers near the Oregon coast. Sixteen weeks later, more than half had died, many eaten by mountain lions. The dams they built were ephemeral and washed away in the higher winter flows.
Still, phenomenon like this are very encouraging:
USGS / Tanya Dewey University of Michigan Museum of Zoology
Then, in the early 1990s, came an accidental experiment. Fish and game officers in Elko, Nevada, were working with ranchers to restore two dried-up stream basins that cattle had obliterated. To recreate a habitat for cutthroat trout, they put fences up – fish on one side, cows on the other. Willow, a favourite beaver food and building material, took root. By 2003, a colony had moved in and begun damming the streams. Before long, the dry creek beds had sprouted into verdant wetlands, which attracted other animals too.
It was never the officers’ intention to lure beavers to Elko, but the events proved that under the right conditions and with very little money, beavers could completely transform an ecosystem.
That same process is now at play at Sugar Creek. The adjacent, undammed creeks are dry in the summer. When they do flow, in autumn and winter, the water moves fast, washing all the dust and nutrients they pick up out to sea. Come summer, it’s just dry gravel again.
At Sugar Creek, on the other hand, the water gets stuck. Beneath it isn’t just rock but rich soil too. NOAA hydrologist Brian Cluer points out sand and fine dirt that has come from further upstream. In the still waters of the ponds, it settles. Grasses, reeds and other plants take root in the stuff, locking it and its moisture in place. With time, a thick base of rich, moist soil builds up, helping to raise the water table.
Cluer says that all this has a huge knock-on effect. The water seeps down into the ground, recharging underground aquifers. That matters because California is depleting its groundwater at an alarming rate. It is now tapping into “fossil” water that has been underground for tens of thousands of years. Farmland is sinking as aquifers collapse. This is the price you pay for an intensive water management system predicated on drained wetlands and artificial channels, says Cluer.
Perhaps a useful way to think about this is that beavers helped shape the world we evolved to thrive in, so returning them to that environment, in which they are so powerful, should not – but does – surprise us when the result is, once again, a positive for the humans in the environment.
So – put the beavers in an environment where they can thrive, step back and let them do their thing. I think this is quite attractive. Hopefully, beaver pelts are not as alluring as they used to be, which resulted in the beavers in California nearly driven into extinction. Leave them alone and start restoring a critical resource.
