- Animals: fish
- Production Systems: agroecosystems, holistic management
Understanding the impacts of agriculture on water quality is an extremely important issue. In the Umatilla basin in eastern Oregon, agriculture is a predominant part of the economy, but concerns about the effect of agriculture on water quality and its impact on local salmon populations is creating much concern about best management practices in the area. The proposed project will develop a means for assessing water quality in the basin through the use of macroinvertebrate community structure. Macroinvertebrates are ideal for assessing water quality because they respond to a variety of pollutants and can rapidly respond to increases in water quality. The proposed project will not only develop the methodologies for using macroinvertebrates in water quality assessment but will also use these methods for assessing the effectiveness of riparian conservation easements on water quality. While conservation easements are seen as a major means of improving water quality, their effectiveness is not well understood. If we are to promote good stewardship of agricultural lands, we must understand the utility of best management practices such as riparian conservation easements.
Agriculturists in the Pacific Northwest are faced with numerous policies and restrictions on the use of their land due to the effects of agriculture on riparian ecosystems; the extent of the impact of agriculture on river systems is not yet quantified and is a matter of debate. There is a growing need worldwide to assess the current quality of aquatic habitats adjacent to agriculturally influenced regions, and to monitor restoration attempts over time to evaluate efficacy (Wright, Moss et al. 1984; Clarke, Furse et al. 1996).
The effects of agriculture on riparian ecology are numerous, and have the potential to highly alter aquatic habitat through a variety of interactions, even in areas that are no longer in use for agricultural purposes (Harding, Benfield et al. 1998; Jiongxin 2004; Fiener, Auerswald et al. 2005). These interactions can affect non-target ecosystems and are generally referred to as non-point source interactions. These effects include, but are not limited to, chemical pollution, canopy removal, and habitat alterations, such as channelization of river beds.
Non-point source (NPS) pollution is a critical consequence of agriculture to adjacent riparian systems (NRC 1996). It can be defined as the accumulation of natural and human caused toxins on non-target systems, such as pesticide runoff effects in groundwater, which is ultimately filtered into the nearby river systems. In agro-ecosystems, pesticides are a prominent source of pollution in aquatic systems and can alter the endemic fauna (Mouvet and Bourg 1983; Young, Onstad et al. 1987; Lijklema, Koelmans et al. 1993; Maher, Batley et al. 1999; Blais 2005). The effects of NPS pollution in aquatic systems have yet to be quantitatively defined in many regions due to the complex interactions of toxicants with substrate and vegetation. Riparian areas have been shown to be effective nutrient sinks and to buffer chemical and sedimentation runoff in agro-ecosystems (Lowrance, Todd et al. 1984; Peterjohn and Correll 1984).
Canopy cover, channelization, sedimentation, and a multitude of other factors affect the variability within the habitat, and play an important role in structuring biologic communities and influencing biodiversity (Hutchinson 1959; Menge and Sutherland 1976; Connell 1978). In consideration of the physical properties affecting habitat selection for optimal population success in organismal interactions, no single factor can be attributed. As mentioned above, microhabitat in the substrate and underlying hyporheic zones influence the biotic community structure with variable substrate stability and micro fluctuations in hydraulic properties (Death and Winterbourn 1995; Brooks, Haeusler et al. 2005). Fine balances between food availability, substrate composition, water quality, physical characteristics, vegetation, and interspecific interactions play a role in the designation of habitat niche (Vodopich and Cowell 1984; Palmer, Covich et al. 2000; Nakano and Murakami 2001). The spatial variability of the combination of factors across a landscape, or river bed, can be attributed to higher survivorship and greater diversity within a habitat, by providing patchy refuge for a greater variety of organisms (Lake 2000). Alterations affecting any of the factors mentioned, such as non-point source disturbances, can impact the biotic communities, throwing off the natural balances within the system.
To assess impacts on river systems that have been impacted by non-point source disturbances, environmental indicator species are utilized to predict habitat quality and overall water quality. Indicator species are organisms that have defined tolerances to different disturbance events, and thus can provide an estimation of the conditions in a graded response to these disturbances (Metcalfe 1989; Peck, Lazorchak et al. 2001). There are a wide variety of life history strategies in lotic environments, and many are well documented. Invertebrate sensitivity to pollution levels and changes in the ambient environment make them excellent candidates for bio-assessment models (Merrit, Cummins et al. 2008). Macroinvertebrates in river systems are also known to have evolved survival and exploitation strategies to living in disturbed conditions (Lytle 2002; Lytle and Poff 2004). It has also been documented that invertebrates in riparian systems can show immediate responses to alterations in the habitat, and that the community succession following a disturbance event can indicate the recovery of the system to natural processes (Robinson, Aebischer et al. 2004). Using macroinvertebrates in the reference areas as the foundation of the relative analysis of test sites and easement property sites will yield an index of habitat degradation along the Umatilla River, and be effective in the construction of a multivariate model that will predict overall habitat quality
The factors affecting riparian systems that exist in agriculturally dominant systems are difficult to measure, because of the variety of potential impact on the river system. Developing a standard model for determining impacts on system health and habitat quality utilizing environmental indicators is critical for better understanding the impacts of agricultural land use.
Outreach: A critical aspect of this program involves broadly impacting the communities near the river by opening lines of communication between researchers and the public. For any effort toward sustainability to be successful, it must be conceived with the intention to involve the communities that are supported by the resources provided by the systems. Without effective communication, any positive results in management will be short lived. By attending local watershed council meetings, writing for local publications, and participating in outreach events, we will make the connection to the community. Through collaboration and communication, the needs of both agriculturist and conservation parties can be included in the solution.
Use of the Model: Recovery of the Umatilla River is an important undertaking not only to conservationists, but also to the people of the Confederated Tribes, as they depend on local salmon populations. The community is dedicated to finding a solution to preserve this unique system. Buffer systems have provided a tentative answer, but their efficacy is yet to be determined. If proven to be successful means of recovery for the Umatilla River, similar attempts can be made statewide, perhaps with even further reaching implications.
The proposed project will assist greatly in determining the effectiveness of conservation easements on improving conditions in the Umatilla mainstem. We expect that the data will show degraded invertebrate communities where the river has been most disturbed by agriculture in comparison to the reference sites, and a strong recovery trend in the regions employing property easements. This research will contribute to the base knowledge of current conditions of the Umatilla River and will have general implications on other systems with similar environmental factors. These implications can then assist in policies that govern land use in riparian areas that can benefit both the salmon conservation efforts and the need of agriculturalists by helping to determine whether conservation easements can be considered a best management practice.