Balancing Ecosystem Services in Semi-Arid Agricultural Lands in an Uncertain Future

Climate Change and Agricultural Intensification in the Umatilla Subbasin of Northeastern Oregon

Principal Investigators: Sandra J. DeBano, David E. Wooster, Don Horneck, and Bruce Sorte

Project Overview:  The goal of this research and extension effort was to begin to understand how select ecosystem services associated with riparian areas and streams in eastern Oregon may respond to two trends likely to impact agricultural production areas in the area in the coming decades: climate change and agricultural intensification (Figure 1). Ecosystem services are simply ecological functions and biodiversity that humans value. Examples include pollination of crops by insects, fish production for human consumption, and clean water in streams. [Click here to read more about how these two trends are expected to impact the Umatilla Subbasin].

We used a combination of modeling and field studies to determine how these two future trends might impact select ecosystem services associated with riparian areas and streams, including steelhead fisheries, stream “health,” predators of crop pests, and native pollinators (Figure 1). [Click here to read more about our methods].

Figure 1.  Schematic of potential effects of climate change and agricultural intensification on multiple ecosystem services associated with streams and riparian buffers.  Dotted lines indicate relationships investigated with modeling. Circles represent taxa related to ecosystem services of interest to managers and policy makers at the watershed level, with filled circles those most likely to be of interest to individual agricultural producers. 

Key Findings

Our studies led to a number of conclusions relative to major groups of ecosystem services and/or their providers in the Umatilla Subbasin.

Beneficial Terrestrial Invertebrates

  • Riparian buffers in the area support significant numbers of terrestrial invertebrates that provide key ecosystem services in these agroecosystems (e.g., pollination, pest control). These invertebrates include a diverse group of native bees, and abundant pest-eating beetles (e.g., ground and rove beetles) and spiders.
  • Maintaining a mix of herbaceous and woody riparian buffers increases the likelihood of maintaining beneficial ecosystem services provided by invertebrates on adjacent agricultural lands. Some beneficial groups, such as native bees, are more common in herbaceous buffers, while others such the predaceous rove beetles, are more abundant in woody buffers.
  • There were not significant differences between perennial or intermittent streams with regard to the abundance of beneficial invertebrates; however, trends indicate that larger scale drying may negatively impact several beneficial groups.

Stream “Health” and Invertebrate Production

  • Buffer size, as measured by length and width, was not related to either biodiversity or stream reach conditions. However, buffer width was negatively correlated to density in summer, possibly resulting from greater shading of streams in reaches with wide buffers.
  • Vegetation composition in buffer areas was related to both biodiversity and stream reach condition. Specifically, the amount of woody riparian vegetation was positively related to biodiversity and stream reach condition in riffle habitat during both winter and summer.
  • In late winter after intermittent stream reaches had resumed flowing (for at least 40 days) biodiversity was lower in intermittent reaches than in permanent reaches. However, in early summer there was no difference between intermittent and permanent reaches, indicating that macroinvertebrate diversity in intermittent reaches eventually recovered after the previous summer’s drying.

Aquatic Habitat and Fisheries

  • Climate change impacted steelhead under all climate change scenarios, primarily by increasing water temperature in the upper reaches of the Umatilla Subbasin, which are important for steelhead spawning and rearing.
  • Agricultural intensification scenarios had weak effects on steelhead and their habitat because most future agricultural intensification is expected to occur in the lower reaches of the Umatilla River, which are already impacted quite heavily by human activity and are currently primarily important only as passages to prime spawning and rearing habitats.   

Management Guides, Publications and Presentations

Data

DeBano, S.J., D.E. Wooster, J. Walker, L. McMullen, and D. Horneck. 2016. Data from: Interactive influences of climate change and agriculture on aquatic habitat in a Pacific Northwestern watershed. Dryad Digital Repository http://dx.doi.org/10.5061/dryad.564q7  - This dataset contains reach-specific data on aquatic habitat in the Umatilla Subbasin for current conditions, six climate change scenarios, and two agricultural intensification scenarios. Variables examined include summer water temperature, low flow, embeddedness, fine sediment, metals in sediment and soils, turbidity, miscellaneous toxins in the water, dissolved oxygen, riparian function, and large woody debris.

Acknowledgements

We thank landowners in the Wildhorse and Mission Creek watersheds for allowing us to conduct the study on their land, Cheryl Shippentower and John Williams for securing landowner permission, and C. Kimoto, A. Madsen, R. Janke, R. Marchosky, and A. Arey for their help in the laboratory and the field. This project was supported by an US EPA Science to Achieve Results (STAR) Program R834566-01.

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