Reducing the impact of summer cattle grazing on water quality in the Sierra Nevada Mountains of California: a proposal

Abstract

The Sierra Nevada Mountain range serves as an important source of drinking water for the State of California. However, summer cattle grazing on federal lands affects the overall water quality yield from this essential watershed as cattle manure is washed into the lakes and streams or directly deposited into these bodies of water. This organic pollution introduces harmful microorganisms and also provides nutrients such as nitrogen and phosphorus which increase algae growth causing eutrophication of otherwise naturally oligotrophic mountain lakes and streams. Disinfection and filtration of this water by municipal water districts after it flows downstream will become increasingly costly. This will be compounded by increasing surface water temperatures and the potential for toxins release by cyanobacteria blooms. With increasing demands for clean water for a state population approaching 40 million, steps need to be implemented to mitigate the impact of cattle on the Sierra Nevada watershed. Compared to lower elevations, high elevation grazing has the greatest impact on the watershed because of fragile unforgiving ecosystems. The societal costs from non-point pollution exceed the benefit achieved through grazing of relatively few cattle at the higher elevations. We propose limiting summer cattle grazing on public lands to lower elevations, with a final goal of allowing summer grazing on public lands only below 1,500 m elevation in the Central and Northern Sierra and 2,000 m elevation in the Southern Sierra.

Ecological impact of transhumance on the trophic state of alpine lakes in Gran Paradiso National Park

“…the United States and Australia), is indeed focused on limiting livestock grazing at lower altitudes or prohibiting it in mountain areas, to preserve water resources (e.g. drinking water quality standard) and high-altitude habitats (Derlet et al, 2010). This debate may even become a conflict in some protected areas such as the Victoria Alpine National Park (Australia), where the decision to permit cattle grazing produced a clash between cattlemen's interests and conservation measures (Fraser and Chisholm, 2000).…”

“…Under moderate grazing pressure, transhumance can improve the biodiversity of alpine vegetation and favor plant and animal species related to the open areas (Laiolo et al, 2004). Mountain aquatic ecosystems are particularly sensitive to livestock presence in their watersheds, due to the small buffering capacity of the alpine vegetation and soils (Derlet et al, 2010). As a result, slight environmental pollution may have a significant impact on aquatic ecosystems since the biogeochemical processes (e.g.…”

“…As a consequence, some protected areas have been established (e.g. Yosemite National Park; Farquhar, 1965) to limit or prohibit livestock grazing in the upper part of the watersheds (Derlet et al, 2010). On the other hand, in many European mountain ranges, the same problems require different and challenging management measures, because of the need for maintaining transhumance to protect the "cultural landscape", which consists of a number of peculiar, unstable ecosystems maintained by the grazing action of livestock and by the traditional pastoral practices (Herzog et al, 2005).…”

“…On the other hand, in many European mountain ranges, the same problems require different and challenging management measures, because of the need for maintaining transhumance to protect the "cultural landscape", which consists of a number of peculiar, unstable ecosystems maintained by the grazing action of livestock and by the traditional pastoral practices (Herzog et al, 2005). To date, most of the studies on livestock impact in mountain aquatic habitats have been carried out in the United States (Derlet et al, 2008;Derlet et al, 2010;Myers and Kane, 2011;Derlet et al, 2012 ), typically approaching the issue from a public health perspective. The aim of the present study is to quantify the impact of livestock grazing on the water quality of high-altitude lakes from a conservation perspective, in an area where transhumance is an ancient, traditional practice, as in many regions of the Alps.…”

An environmental assessment of United States drinking water watersheds

“…Swartz et al (2003) found a positive relationship between the amount of residential land use and drinking water nitrate concentration. Derlet et al (2010) proposed changes to the cattle grazing system in the Sierra Nevada Mountains as a means to further protect drinking water drawn from the area. Mehaffey et al (2005) showed that small decreases in urban and agricultural land in the drinking water watersheds for New York City led to detectable improvements in water quality.…”