Mitigation of impacts of cattle access on stream ecosystems -- efficacy
of fencing
Abstract
Headwater streams can constitute up to 80% of river channel length and
are vulnerable to anthropogenic pressures due to their high connectivity
to adjacent land, large relative catchment size and low dilution
capacity. In these environments unrestricted cattle access is a
potential significant cause of water quality deterioration, resulting
from increases in stream bank erosion, riparian damage and sediment
deposition among others. Several studies have reported improvements in
physico-chemical and hydromorphological conditions of streams following
elimination of cattle access; few, however, have focussed on the
ecological impacts of such management practices. Here, such impacts are
assessed. We look at the short-term effects by comparing habitat
condition, sediment deposition, and instream macroinvertebrate
communities upstream and downstream of cattle access points prior to,
and one year following exclusion via fencing. The long-term effects are
also measured by reassessing a small stream catchment entirely fenced
off from cattle access in 2008 under a concerted management effort. In
the short term, cattle exclusion led to reduction in deposited sediment
downstream of cattle access points and a related homogenisation of
macroinvertebrate community structure between upstream and downstream
sampling points. Increased abundances of specific indicator taxa (
Ancylus fluviatilis, Glossosomatidae and Elmidae) in the fenced
catchment following 9 years of exclusion highlight the long-term
ecological benefits of such mitigation practices. These findings
highlight the importance of incentivised agri-environment schemes in
reducing the negative impacts of cattle access to these vulnerable
ecosystems.