Our Urban Ecosystem

by Mark Goldschmidt

Our mountain backdrop has changed little, but 150 years ago paleo-Altadena was virtually barren of trees, only seasonal grasses, chaparral and poppies covered the gravelly outwash. Then wells were dug and water was channeled from the front range. With water came first crops and trees, then gardens, more trees, streets and houses. Over the years a rich environment has developed that supports an interesting variety of wildlife, creatures that lead their own lives in what we consider our neighborhood. The big trees and old homes buried in shrubbery that make Altadena such a charming place also provide cover and nesting places, and irrigated landscapes provide food and water in abundance. In this mosaic of backyards and gardens, the urban ecosystem thrives.

Altadena’s urban ecosystem includes animate life ranging from soil organisms to giant trees, from insects and worms to birds, raccoons and coyotes –– prey and predators. It is not a very stable ecosystem (few are), it depends on constant inputs from us humans. A habitat in an overgrown back yard can be wiped out in a day when an ADU is built. Or poison set out to kill rats can wipe out predators like coyotes and crows who scavenge the deadly carcasses. Fewer coyotes, major consumers of rodents, allow the rat population to increase dramatically. Diseases sweep through periodically, causing die offs. Raccoons are currently in deep decline due to distemper.

Habitat varies greatly across Altadena. Near the urban edge large animals — bears, deer, mountain lions — live up the mountain and come to town to forage. There is a greater variety of birds at the edge, and other shy creatures that can’t survive urban life, like foxes, snakes, wood rats, and native squirrels.

Down slope, where Altadena melds into the Pasadena grid, older mature neighborhoods offer a patchwork of habitat types. Overgrown yards, with abandoned vehicles, piles of construction debris, or broken down sheds, offer prime cover and denning opportunities; well kept yards provide ponds, pools, and a rich forage of fruits, grasses, and herbs. Garbage is a minor source of food for Altadena’s urban wildlife. The range of fauna is poorer here, many are introduced species that join with native ones adapted to urban life. These are wild creatures in our midst in an ecosystem with a hierarchy of predators and prey.

Ecosystems, even poor ones like our urban habitat, are complex. Scientists spend careers unraveling the relationships, dependencies, and governing factors in natural systems. It is not possible in our newsletter to delve into these dynamics even if we were qualified, which we are not. Instead, we have looked at some of our larger wild neighbors and tried to give a feeling for what their lives are like, and a glimpse of how they interface with ours. We left out many important major mammals, skunks, deer, bobcats to name a few, but information about individual species is easily available on line.

We barely touched on birds, perhaps the subject for another issue.