Road Ecology

While roads connect people and activities in the built environment, they often divide and pollute living networks of ecosystems. With respect to the Los Angeles River, this is a pervasive issue, particularly with respect to major highway systems like the 101 and the 405 which run parallel to the river. By way of example 1 in 5 of the iconic California Mountain lions are killed by car strikes1 and have been in a state of perpetual decline as their numbers and genetic diversity decline in the Santa Monica Mountains.2 Roadway infrastructure is fundamental to the modern economy and to connecting communities; however, it has become a singlepurpose solution at the expense of multiple uses and needs within the landscape.

At present Los Angeles County has over 20,000 miles of roadway3 but the infrastructure has come at a significant cost to ecosystems. As noted ecologist Richard Forman describes in the book “Road Ecology”, the scale of our roadway networks have become such a dominant feature in our landscape that their interactions with the natural environment have become their own branch of study.4 Caltrans and researchers at UC Davis are currently exploring alternative strategies to reconnect living ecosystems across existing, traditional transportation barriers, which could be instrumental in adapting existing infrastructure for broader benefit of animal and human communities alike.5

The Los Angeles River is fundamental to rebuilding living corridors and transforming adjacent roadway infrastructure to better connect the river to adjacent neighborhoods and to essential range for birds and range mammals, reptiles and amphibians. To overcome the challenge of transportation barriers, such as highways, two tracks of investigation may be necessary: the diversification of modes of travel to relieve pressure from the highway system, and the adaptation of existing infrastructure to accommodate additional paths and scales of connectivity.

In the map below, “Significant Ecological Areas,” as defined by the Los Angeles County GIS Portal, call out important reaches of ecological richness; however, there are other areas within LA County that play important roles in the ecological community. For example, the Elysian Valley or the Los Angeles River algae mat both have been identified as having significant areas of biodiversity for terrestrial and migratory species.


1 Wildlife Research Institute, Wild News, (2015)
2 Adam Popescu, Scientific American, Santa Monica’s Mountain Lions Are Stuck on an Island, and Fast Disappearing, http://www.scientificamerican.com/article/santa-monica-smountain- lions-are-stuck-on-an-island-and-fast-disappearing/ (November 2015)
3 Los Angeles Almanac, http://www.laalmanac.com/transport/tr01.htm (April 2016)
4 Forman, Sperling et al., Road Ecology, 2nd Ed, Island Press, (2002)
5 Road Ecology Center, University of California at Davis, http://roadecology.ucdavis.edu/partners/caltrans