Of Rats and Regrowth

The Gap Fire, the Jesusita Fire, the Tea Fire — this is a litany that can still bring shudders to most residents. A drive-by of affected areas reveals lots of new homes finally finished and occupied, and more that are still in process of rising from the ashes. As for the vegetation, it, too, is rising from remnants of woody plants like oak trees, ceanothus, lemonade berry (Rhus integrifolia), and many more. Other colonizers (or recolonizers) are sprouting from seed or underground tubers and bulbs.

It’s easy to find inspiration from this phoenix-like rebirth. One such species rising from the ashes is Calystegia macrostegia, the California morning glory, which, according to Steve Junak at the Santa Barbara Botanic Garden, is doing “an amazing job controlling erosion on the steep hillsides.” This vigorous vine has seemingly been overtaking anything else that puts up a stem or branch. Where did it all come from and why is it in such abundance now?

California morning glory is a perennial, so in the mild climate of Southern California, not only can it flower and produce seed during the growing season, but it can also persist from year to year. The root system can be extensive, going as deep as the arable soil is (up to 18 feet). The current proliferation of this species in the local chaparral community is probably a result of this ability, as well as a storehouse of seeds that have been lying under the shade of the shrubs for decades. A long and abundant rainy season this year coupled with the increase in sunlight reaching the soil were the perfect combination for a population explosion from persistent roots as well as seeds.

The appearance of this and other somewhat ephemeral species of natives is evidence that a new succession has been started. It will take a few more years before the chaparral shrubs will once again shade out the annuals and soft perennials. All of this is a normal progression and will probably result in a return to a relatively normal distribution of plant species.

Plants are not the only organisms that respond to catastrophic events. Animal populations also wax and wane in response to the availability of habitat and food sources. Human residents adjacent to recently burned areas are well aware of this fact. The most obvious result has been a really impressive increase in the number of rodents. Rats — including the native wood rat, Neotoma fuscipes, and Rattus rattus, known as the black rat — are threatening to overrun gardens, garages, and homes. Basically unafraid of humans, these creepy fellows seem to have become even more blasé this year. Wood rats are nesting wherever they please, from the shrubbery in otherwise well-groomed gardens to the engine compartments of vulnerable vehicles. Other rodents are also on the rise: Gophers are being consumed in record numbers by birds of prey (including the impressive great blue heron), and cottontail rabbits brazenly attack tender vegetables and flowers just inches from the front door.

The key to understanding that Nature always finds a balance is remembering that the pendulum swings from extreme to extreme. The current situation is a boom for some species in the wake of a near-bust for others. This, too, will change. The raptors will lay larger clutches of eggs, and the coyotes will den more hungry kits to utilize the new food resource. The ceanothus will bloom in spite of the bindweed, and the oaks regrow their leaves to once again provide shade.