Central Valley

Change in Land Use

Effects of Land Use & Climate Change: Resurveys in the Central Valley and Urban Areas

"The whole country is being settled up, since the L.A. Aqueduct has brought water within reach; and even the stony washes are mostly cleared of cactus and brush and set out to fruits or track-gardened. It looks as tho the desert fauna and flora of San Fernando Valley were entirely doomed; it must be studied at once if the record is to be preserved."
Joseph Grinnell
15 September 1917
Tujunga Wash, Los Angeles, CA

While some parts of California have been carefully protected from human development over the past century, others have experienced phenomenal growth in agriculture and urban sprawl. Climate change and habitat conversion by humans are two of the greatest threats to biodiversity both in California and globally. How these two drivers interact to shape species distributions remains a complicated puzzle. Human land-use change may exacerbate climate-driven range contractions and extinctions by fragmenting corridors through which species can track suitable climates, or by reducing the area of natural habitat available for future range expansions. On the other hand, closely cultivated agricultural fields and suburban parks may provide stable refuges from the effects of changing climates for species that can tolerate some level of human disturbance.

To better predict future extinction risk and changes in community composition, it is critical that we identify the degree to which climate and land-use change have synergistic versus agonistic effects on species distributions, as well as how this relationship varies across species with different functional traits.

We will initiate this portion of the Grinnell Resurvey Project by conducting bird resurveys from 2015-2017. It will be led by Ph.D. student Sarah MacLean and Prof. Steve Beissinger. We will quantify changes in bird distributions across a gradient of both natural and human-modified landscapes in the California Central Valley and southern coast. We will resurvey birds at 100 sites originally visited by Joseph Grinnell and colleagues at the UC Berkeley’s Museum of Vertebrate Zoology between 1900 and 1930. Previous resurveys by the Grinnell Resurvey Project have largely focused on protected areas. Resurveys in the Central Valley, Los Angeles Basin, and San Francisco Bay Area will break new ground for the project by incorporating sites that have undergone significant agricultural and urban development, and will complete coverage of bird resurveys throughout California.

By quantifying site-level turnover (i.e., colonization and extinction) of avian species across a diverse gradient of both climate and land-use change, we will elucidate the effects of these drivers of change in bird distributions, both historically and into the future. Our key questions are:

  1. How has land use changed in California, and can these changes be accurately captured by predictive models?
  2. How do additive and interactive effects of changes in temperature, precipitation, and land use, and the functional traits of species drive changes in site-level turnover across bird species?
  3. How will bird distributions in California respond to climate and land-use change over the next 50 years?