Data and R code from: Relics of beavers past: time and population density drive scale-dependent patterns of ecosystem engineering

Like many ecological processes, natural disturbances exhibit
scale-dependent dynamics that are largely a function of the magnitude,
frequency, and scale at which they are assessed. Ecosystem engineers
create patch-scale disturbances that affect ecological processes, yet we
know little about how these effects scale across space or vary through
time. Here, we investigate how patch disturbances by beavers (Castor
canadensis), ecosystem engineers renowned for their pond-creation
behavior, affect ecological processes across space and time. We evaluated
how beaver population recovery influenced surface water dynamics in
relation to population density over 70 years across multiple spatial
scales (pond, watershed, and regional) in northern Minnesota. Surface
water area was positively related to population density at the watershed
scale; however, despite variation in beaver densities (and therefore
surface water area) at the watershed scale, regional-scale surface water
area was stable through time. This stability appears to have been driven
by asynchronous beaver density fluctuations among watersheds, combined
with the increasing importance of abandoned ponds. Beavers initially
created and occupied larger ponds with greater surface water area, but
through time shifted towards occupying smaller ponds. As ponds accumulated
on the landscape proportionally more surface water was stored within
abandoned ponds, which offset the smaller size of occupied ponds. Beaver
engineering—driven by density-dependent mechanisms and the legacy effects
from abandoned ponds—not only follows general patterns of patch
disturbance dynamics by creating a spatial mosaic of patches, but the
organism-created mosaic also appears to generate ecological stability at
greater spatial scales. We suggest restoring beavers to landscapes is a
viable method for increasing surface water storage and will ultimately
help advance numerous conservation and rewilding objectives. Our study
demonstrates that ecosystem engineering effects can be scale-dependent,
indicating researchers should evaluate the ecological impact of engineers
across diverse spatiotemporal scales to fully understand their functional
roles in ecosystems.