[This summer Oregon Wild has had the great pleasure of hosting a handful of outstanding interns.  Supportive of both our development and conservation programs, they’ve been doing research, outreach, and more.  Among the tasks our Healthy Rivers intern, Dylan Cerling, completed this summer was a summary of recent research on climate change impacts to the Klamath Basin, including the latest study be the University of Oregon and National Center for Conservation Science and Policy.  Below is Dylan’s helpful, but frightening summary on what we might expect in the Klamath.  (This summary is not for public use or reproduction.)]

Both the causes and effects of climate change are complex; models by their very nature may fail to account for certain processes or predict certain outcomes.  However, models consistently suggest that the net effect of climate change on fish and wildlife, and their habitats in the Klamath Basin will be harmful, as water levels both drop and become more variable, and stream temperatures rise.  

By the year 2100, anthropogenic global climate change is, depending on regulatory actions, estimated to raise global temperatures from 1.1 to 6.4 degrees C. While the Klamath Basin has temperatures and precipitation levels that vary widely according to geography and season, it is a generally dry region and climate change is expected to exacerbate this status. Predictions of yearly precipitation are variable under different models; but even so, all models agree that warmer season precipitation will decline.

Although summer flows are often already extremely low in the Klamath Basin due to the demands of irrigation, further decline in summer flows can be expected through decreased summer precipitation and warmer air temperatures year-round. As mean annual temperatures increase, more precipitation during the fall, winter, and spring will fall as rain rather than snow, reducing snowpack and limiting water stored as snow for release during warm summer months. The shorter snowpack melt season will also result in unsuitable perennial side channel and floodplain habitats that are currently used by basin salmon, like endangered coho and Upper Klamath-Trinity Chinook.

The natural hydrograph of Klamath Basin rivers and streams will be further altered under climate change conditions as flood events increase.  Higher rates of peak flows will occur during the winter and scour streambeds, killing salmon eggs. The National Academies of Science has estimated a much higher rate of salmon egg mortality as temperatures warm.

Lower flows, particularly in combination with higher air temperatures and lower rates of snowmelt, will result in higher stream temperatures; such higher stream temperatures have a wide variety of negative effects on salmon, including increased disease vulnerability and presence, lower levels of dissolved oxygen, and outright mortality.

Climate change and resulting higher temperatures will affect water quality in other ways as well. Harmful algal blooms are expected to take place earlier, last longer, and occur at higher intensities. As we know from summers rich with green reservoirs in the Klamath, harmful algal blooms often release toxins which are dangerous to both fish and land animals, and further decrease levels of dissolved oxygen in the water.

Climate change is also predicted to cause increased sediment levels in the region. As storm events become more frequent and intense, and as more precipitation during the winter falls as rain rather than snow, streams will receive more eroded fine sediment. Higher levels of nutrients deposited through erosion will increase algal blooms. Sediment deposition will lead to suffocation of salmon eggs and alevin. Increased sediment will also lower the productivity of stream overall, as clarity decreases and less light reaches necessary primary producers, decreasing the life the stream can support.

Flows from springs fed by groundwater are likely to decline due to climate change, with some smaller springs potentially disappearing entirely. As these flows are often cooler than main stem river flows, temperatures will continue to increase and essential cold-water refuges for fish will be further limited. Furthermore, as the region’s agriculture becomes increasingly dependent on groundwater for irrigation, as seen during the 2010 drought, there will be less groundwater recharge and supplemental flow into regional rivers.

Apart from the direct affects of climate change on water ecosystems, terrestrial ecosystems will also be affected in the Klamath Basin. It is very possible that as precipitation and temperature patterns change, redwood and spruce tree communities will decline or disappear. This, in turn will affect fish habitats, as the large woody debris that create important holding pools for the fish may decline. Range shifts may happen rapidly, facilitated by disease and insect outbreaks, as well as increased rates of wildfires, which are expected to increase due to warmer winters and lower water levels in the summer.

Climate change is also expected to have widespread effects on terrestrial ecosystems; for example, noxious, invasive species will likely increase in abundance, and it is possible that some species of plants and animals will decrease greatly. Species relationships may be disrupted as timing behavior shifts. Finally, it is likely that wetlands and riparian habitats will decrease generally, even more so from the basin’s existing 80% loss from early agricultural development.  

Over the next several decades, the effects of climate change will be strongly felt in the Klamath and Trinity Basins. Rivers, streams, and their inhabitants will be particularly affected, and fish and wildlife will likely need strong protective management actions in order to withstand these changes.