Friday, August 5, 2011
There's an old story that if a biochemist wanted to figure out a locomotive, step one would be to blow it to smitherinos. The reductionist approach works pretty well for cells. Pulverize, separate, and do experiments to figure out which pieces fit together and how they help the metabolism of the cell hang together.
Gorongosa got pulverized during the civil war. Rebel and government armies surged back and forth over the park for years. Armies on the move are tough on herds, and soon enough there were no more herds, and finally almost nothing left standing. Crocs got through by hiding under water. There is nowhere for a water buffalo to hide from a hungry battalion of soldiers.
That grim time wasn't reductionism, it was just reduction. It was also a long time ago. And it turns out there is a lot to learn from studying the disassembly and revival of the hypervital living economy of Gorongosa. Life is surging here now and the metabolism of the park is putting itself back together again fast. But there is still a huge experiment to be done in Gorongosa as the reboot of the place progresses. That's going to be a big theme in Life on Earth. We're writing it up now and we're going to be following it for years in our future editions as we report on the progress of Greg Carr and his team as they reassemble Gorongosa National Park.
This week ecologist Marc Stalmans gave the textbook project aerial lectures on transition zones in the park--floodplain to copse to forest and so on. It's all about water. But it's also about succession. If grazers don't mow the grasses, browsers don't flourish. If browsers get befuddled, alien things like mimosa move in and grow too tall. The grazing grounds flinch and withdraw. Environmental change is as normal as the day, especially here, and that leaves park managers with countless decisions about how Gorongosa emerges from its recent history.
Human influence can be measured in units of mass and volume of waterborne material pouring into the park from the mountain and from a huge catchment in the northeast. The volumes are rising due to land-use changes outside the park. The sediment is filling in Lake Urema, the heart of Gorongosa's circulatory system. As the lake becomes too shallow, the hippos move elsewhere, taking with them massive activity that stirs up the lake. With their exodus, sediment settles and the lake bed rises.
There are interveners and leave-aloners here, and often after a couple of years working in the park they switch sides. The science is complicated. It was once thought that the lake was fed almost entirely by runoff from higher terrain. It now seems plain, based on isotope comparisons and other techniques, that the lake is sustained by water transfer across a porous stratum between the lake and the aquifer. The surprising discovery was made that more water arrives from the upper catchment than from the mountain. The lake could easily be remodeled by dredging parts of it, which might bring back the hippos, and one learns to trust the power of hippos to model their environment. Water pileups could be created at the outlet. Sediment could be captured on the higher ground by porous barriers. Or the entire scene could be left alone to shape itself according to the laws of nature, with "nature" here meaning a beautiful scene mangled not so long ago by war and now recovering while inhaling the smoke and tailings (goldmines in the buffer, fer criminy's sake) of escalating human impact on the surrounding region.
We're heading out in the truck this afternoon to finish Marc's aerial transition-zone lessons with shoots at the same sites on the ground. We'll cross-cut the shoots with maps and animations to make a lesson that will shock the children awake. One of these days, one of those kids is going to be making decisions about hydrology and hippos at Lake Urema.