There is no disputing the fact that the number of salmon return to spawn in the rivers and creeks of the Pacific Northwest are mere fractions of historic levels. In our search for the cause we have coined catchy phrases like "the 4 H’s", referring to habitat, hydropower, hatcheries, and harvest. So now we move on to improving habitat, removing dams, reforming hatchery practices, and revamping the way we harvest fish. But will all of this have the desired effect of restoring salmon runs to historic levels? One aspect of this crisis that has not received the attention it warrants is the effect of the loss of biodiversity on the salmon runs. Not only have we directly effected the world of the salmon through the 4 H’s, but we have unwittingly created a number of other less conspicuous problems as our actions have combined to undermine the salmon’s survival.
Biodiversity is a measure of the complexity and richness of an ecosystem. So, the loss of biodiversity is the loss of complexity, making the ecosystem homogeneous. In our attempt to supplement the diminishing populations of salmon with hatchery stocks, we have decreased the genetic diversity of entire runs. This decrease in genetic diversity has led to numerous problems, not the least of which is the increase in diseases and parasites. It is this homogeneous nature that brings about some of the worst problems. As Yvonne Baskin points out in The Work of Nature, some of the most dramatic disruptions to a community are caused by invasions of exotic pests, parasites and pathogens. And in the case of a more homogeneous run, larger numbers of fish are susceptible to a single parasite or pathogen allowing it to wreak greater havoc on the run. The possibility also exists that through our influences, some evolutionary significant units of salmon may have already become extinct. This has the same effect that introducing hatchery fish into the wild has, the reduction of genetic diversity. The reduction of genetic diversity is but one way humans have inadvertently introduced stresses into the lifecycle of salmon.
The effects of logging are evident to anyone driving in Western Washington or Oregon. Clear-cutting practices have striped large tracts of land bear of forestation leaving the ground unprotected from the forces of nature. The ugliness is only aesthetic it is the effects it causes that are troubling. Clear-cut land and the watersheds they occupy are much more prone to increased stream volumes and even flooding. Increased stream volumes can do tremendous damage through scouring. Scouring removes the essential elements of salmonid habitat including gravel and large woody debris. Since there is nothing left to slow the flow of water, erosion increases which in turn increases the sediment loading in nearby creeks and rivers. Increased sediment loads turn the gravel bottoms of the creeks and rivers into mud covered sluice pipes. Without clean gravel, salmon have no place to spawn.
Lumber is not the only incentive for clearing land. For decades man has cleared land in the name of progress. Whether it was for building or for agriculture, it changed the nature of the surrounding landscape forever. When agricultural fields were cleared, single crops were planted, greatly reducing the complexity of the area. Single crops invite so many other problems such as pest infestation and soil depletion. When a more complex field or forest was in place, pest infestations were dealt with through a series of checks and balances. The large number of different plants attracted large numbers of insects. These different insects helped to keep their populations in check through predation. But when a single plant species attracts a smaller number of insects, there is no predation and the population of the insects grows unchecked. So man developed pesticides to combat the infestations. While these pesticides are not harmful to the plant species the are applied to, they can cause great harm to wildlife. In our efforts to maximize the use of agricultural land, we plant crops as close to the edge of the land as possible and in some cases, this means it may border a creek or river. This is the situation that can cause the greatest problems for salmon. Pesticides may drift when applied directly into the water. Even when the agricultural lands do not border creeks and rivers, the pesticides can still find their way into the water by leaching into the ground water and eventually into the creek. When man clears land for development purposes, a completely different set of problems arises. As more and more pavement is laid, the land becomes more and more impervious to water. In effect, the parking lots and roads become large catch basins, funneling water into the storm water collection systems and away from the creeks and rivers it used to drain into. This causes extreme fluctuations in conditions. In periods of normal or less than normal precipitation, creeks and rivers may run dry and when there is precipitation, it takes less to cause the creeks and rivers to flood.
The influences man has exerted on the salmon are causing a decline in the populations of many species. But there is another way to look at the loss of salmon – from the perspective of other wildlife that depends on the salmon. The decline in the number of salmon greatly effects bears, eagles and other smaller predators that count on the salmon as a major source of food. Salmon also serve as a source of nutrients to other fish in the creeks and rivers. When they die after spawning, they stay in the water and decay, increasing the amount of organic material in the water. We must make sure that we do not lose sight of this perspective and try to save the salmon for us. We must save the salmon for them and for the rest of nature first. If we are once again able to take advantage of the abundance of the salmon once again, all the better for us.
Mike Rechner
The Face of Salmon