Projected impacts of climate change on salmon habitat restoration

Abstract

Throughout the world, efforts are under way to restore watersheds, but restoration planning rarely accounts for future climate change. Using a series of linked models of climate, land cover, hydrology, and salmon population dynamics, we investigated the impacts of climate change on the effectiveness of proposed habitat restoration efforts designed to recover depleted Chinook salmon populations in a Pacific Northwest river basin. Model results indicate a large negative impact of climate change on freshwater salmon habitat. Habitat restoration and protection can help to mitigate these effects and may allow populations to increase in the face of climate change. The habitat deterioration associated with climate change will, however, make salmon recovery targets much more difficult to attain. Because the negative impacts of climate change in this basin are projected to be most pronounced in relatively pristine, high-elevation streams where little restoration is possible, climate change and habitat restoration together are likely to cause a spatial shift in salmon abundance. River basins that span the current snow line appear especially vulnerable to climate change, and salmon recovery plans that enhance lower-elevation habitats are likely to be more successful over the next 50 years than those that target the higher-elevation basins likely to experience the greatest snow-rain transition.

Fig. 1.

Modeling domain and climate data locations. Numbers show the meteorological observation stations used to generate input data for the hydrologic model.

Fig. 2.

Model linkage scheme.

Fig. 3.

Climate impacts on three hydrologic variables. (A1–A3) The results of the GFDL R30 climate model. (B1–B3) The results of the HadCM3 model. (Top) Percent change in incubation peak flow. (Middle) Percent change in minimum spawning flow. (Bottom) Change in prespawning temperature in degrees Celsius. The basin-wide average change is shown in the lower left corner of each figure. Black lines delineate subbasin boundaries. All simulations used the “current” land use scenario.

Fig. 4.

Basin-wide percent change from 2000 in numbers of spawning Chinook under different combinations of climate change and habitat restoration for the GFDL R30 (A) and HadCM3 (B) climate models.

Fig. 5.

Change in spawning Chinook salmon abundance between 2000 and 2050 under three future land-use scenarios. (A1–A3) The results of the GFDL R30 climate model. (B1–B3) The results of the HadCM3 model. (Top) Current land-use scenario. (Middle) Moderate restoration scenario. (Bottom) Full restoration scenario. The basin-wide total change appears in the lower left corner of each figure.