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Van Beacham lives in northern New Mexico and has been fishing since he was 6 years old. He has been a professional fly fishing guide for over 20 years in southern Colorado and south-west Wyoming. Over the years he has witnessed many of the effects that warmer temperatures are having on the river systems and the fish that depend on them.
I have been witness to many of the effects that warmer temperatures are having on the river systems and the fish that depend on them.
As a kid I remember the wet cycle when we had greater than average snow pack and lower temperatures. This was from about 1970 up into the 1990s when the snow stuck around all winter long. We never had spikes of 60ºF (16ºC) degree weather in January like we do now.
Some of these wet/dry cycles we know are natural. What is different over the last ten years or so is that temperatures are way above what we ever saw before. Around Albuquerque, New Mexico, for example, we’ve lost a month of winter — a month of time between the last frost and the first frost.
In the Rocky Mountain west and further north there has been even more changes. At high elevation (greater than 5000-7000 feet, or 1500-2100 metres) I’ve been seeing temperatures 5-10ºF (2-5ºC), sometimes even 25ºF (12ºC), warmer than average.
Earlier snow pack runoff
We are losing snow in a time of year when we should be gaining it. This has been the story for the last 8-10 years, and it’s getting worse and worse. Recently, we had lots of snow — slightly above the average — but it was so warm that the runoff happened much faster than normal and was over by June and July. The rivers were all raging and, instead of a slow sustained runoff, they peaked violently and then dropped down to a trickle by early summer.
Some streams and small rivers have been drying up completely. I believe that some of these patterns can be explained by the natural drought cycle that we are in. Also, there is continued pressure from development in some areas. But, how do you explain the fact that, in four generations, none of these streams have ever dried up?
I think you have to look at the consistent warmer temperatures that we’ve been having and recognize that what’s going on is an interaction between drought, development and global warming.
Effects on Fish
When the low stream flows combine with warmer temperatures, the fish really take a hit.
For example, the spawning season has been changing because the fish won’t spawn when the water is too hot. The timing of the aquatic insect hatchings has also changed and for wild trout, these insects are really important.
I used to go out fly fishing a lot in the middle of summer — July and August were our busiest times. But now the fish are literally so sluggish that they can’t feed. During the last few years, some parts of Montana have been closed for fishing in July and August. The fish were just too stressed and some were dying. Water temperatures greater than 70ºF (21ºC) starts to kill fish.
Algal blooms, increased sediment loading and more aquatic weeds are all things I’ve been noticing more and more. These changes hurt the fish and it takes a toll on the wild trout first. In the lower reaches of some of the streams I fish, only the brown trout are hanging on. There is also another shift going on. In some areas the cold water loving trout are disappearing altogether and are being replaced by small mouth bass, which can tolerate warmer water temperatures than trout.
Low stream flows and increased water temperatures have become a double-whammy for the trout fisherman. As a fishing outfitter, I’ve had to reposition the way that I guide. I’ve learned to lease private waters that are either higher up in elevation or below dams so that I can have a long enough season. I don’t fish in the summer much at all and winter fishing is becoming more popular. Overall, the last five years business has been down.
People won’t pay me to take them out bass fishing. Folks can fish for bass in a lot of lakes and reservoirs around the country — It’s the fly fishing for wild trout that draws people to these mountain streams.
Sometimes I tell my clients things they don’t always want to hear. I’m honest about why the fishing is poor in some areas and I feel it’s my duty to talk about the problems. I let people know that we’re partly responsible for the warming of the globe. This shocks some people. Before, many of them did to not believe that humans have a role in climate change, but now folks are starting to understand this relationship and are seeing the big picture.
Scientific reviewReviewed by: Dr Patrick Mulholland, Environmental Sciences Division, Oak Ridge National Laboratory, USA
Many of the observations described by this witness are consistent with measurements made by scientists over the past several decades and reported in the scientific literature. Further, these witness observation are consistent with projections of future changes in climate for the western U.S. based on global climate models. In particular warmer winter temperatures and earlier onset of the spring melt are predicted to result in lower summer baseflows in streams and rivers in the in the Rocky Mountain region.
A recent paper in the prestigious scientific journal Science by Barnett and others (February 22, 2008 issue) documents many of these climate and hydrologic changes in the western U.S. over the past several decades and shows that these are almost certainly the effects of human-caused climate change. These authors then describe a number of severe water supply problems that are likely to result from continued climate change in this region. There are other studies that predict that fish populations will be negatively impacted by these hydrological changes together with warmer summer water temperatures as described by the witness.
Van Beacham’s observations of poorer fishing in summer months are consistent with these predictions, although I do not believe there have been definitive studies yet that have shown this is already occurring. And his observation of more noticeable algal blooms is also consistent with projections of climate change effects. In another recent paper in the journal Science, Paerl and Huisman (April 4, 2008 issue) have shown that harmful algal blooms are favored by low flows and high water temperatures in many freshwater and estuary systems and may increase in frequency and severity with projected human-induced climate change.
- Barnett, T. P. and 11 co-authors. 2008. Human-induced changes in the hydrology of the western United States. Science 319:1080-1082.
- Paerl, H. W. and J. Huisman. 2008. Blooms like it hot. Science 320:57-58
All articles are subject to scientific review by a member of the Climate Witness Science Advisory Panel.