Keitreice Kirksey and Dr. Emily Fairfax recently released their Preliminary Study of the beavers on the Salinas River.
Below is the text of the poster above by Keitreice Kirksey and Dr. Emily Fairfax:
Can small paws make big changes on big rivers?
Beavers are well known ecosystem engineers that help sustain many wildlife,
create and widen riparian wetlands, attenuate floods, buffer droughts, and
create a habitat that supports and protects many species. These things are all
possible due to how beaver dams and canals slow, spread, and store water in
both surface water and groundwater. Beavers typically are most active on small
streams where their engineering is obvious, but they are also present on large
rivers. The scale of their impacts in these larger hydrologic systems is less
understood. Beavers recolonized a site on the Salinas River, a big and sandy
river in Central California, and we saw an opportunity to monitor changes – do
their dams and canals still provide the same benefits that are often observed on
Game Camera Monitoring
• Two camera traps set up near beaver dam, videos retrieved ~2x/month
• Reviewed footage and created dataset of animal occurrences over time
Field Visits and Photospheres
• Ten visits to field site during study – photosphere (360 photo) taken at each
• Note locations of dams and dam condition during visits
• Landsat 8 and Sentinel 2 NDVI (Normalized Difference Vegetation Index) to
monitor plant productivity over time
• SPEI (Standardized Precipitation Evapotranspiration Index) for drought
monitoring over time
The study took place on a 2.44 km section of the Salinas River in Atascadero, CA. The site is adjacent to open space,ranches, and a water treatment plant.
Beavers Increased Riparian Productivity Despite Intensifying Drought
Over the last five years, beavers have consistently increased
the productivity of nearby riparian vegetation (Fig 3)
• This happened despite 2020 and 2021 being droughts periods
• We determined correlations between the number of beaver
dams, the drought index, the winter (off-season) NDVI, the
summer (growing season) NDVI, and the Year.
• Growing season NDVI had a negative correlation with SPEI –
the riparian zone got greener and denser while the drought got
The Big Picture Story
We used publicly available satellite and aerial imagery between 2004 and
present to count the number of satellite-visible beaver dams in our study
area. We also calculated the SPEI as a measure of drought conditions
during that time
We found that the SPEI did not have a significant relationship with the
number of beaver dams or the change in the number of beaver dams
(p > 0.05). A lethal trapping permit was issued and executed in the study
area around 2017 which could explain the dramatic population crash during
Generally, the beavers in this area have created and maintained disturbance resistant wetland habitat for the majority of the last 17 years. The other portions of the Salinas do not have the same observed drought resistance or biodiversity.
See the Changes Yourself!
Numbers and p-values are great, but actually seeing the study area
change is what convinces a lot of folks that beavers are powerful
ecosystem engineers. You can see some of our game cam highlights for
yourself at: bit.ly/SalinasBeavers or by scanning the QR code below
This project was supported by a research grant from Biodiversity First! and the National Science Foundation HSI-SMART grant. This material is based upon work supported by the National Science Foundation under Grant No. 1928693. Special thanks to our funders, SLO Beaver Brigade, Joe, Calvin, and Brandon!