For next Thurs: Jackson et al Historical overfishing and the recent collapse of coastal ecosystems. Science 293:

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1 For next Thurs: Jackson et al Historical overfishing and the recent collapse of coastal ecosystems. Science 293:

2 Resource: means of supplying a want or deficiency, from French resourdre "to rally, raise again" Everything living uses resources Use of resources dictated universally by competition among and within species Everything else vs. Humans Pre-industrial vs. Industrial (technology, power & governance)

3 Ludwig et al Why and how does over-exploitation happen? 1. Wealth (from resources) = social and political power, which promotes increased exploitation.positive feedback gold rushes.. 2. Scientific understanding limited by lack of controls/replicates (scientific management of optimal exploitation perspective) 3. Complexity of systems precludes a reductionist approach so trial & error is needed 4. Natural variation (in abundance) masks over-exploitation, often until severe & irreversible See all these components in following case study. Ludwig et al. 1993

4 Case study from: National Academy of Sciences Upstream. Salmon and society in the Pacific Northwest. Pacific salmon have declined dramatically in the Columbia River Basin over last 150 years - direct result of resource overexploitation and development of the river. Extensive recovery efforts have been unsuccessful.

5 The Columbia River Basin is the dominant water system in the Pacific Northwest, draining an area the size of France. The river provides power, food (through irrigation), transportation (through navigation), recreation, fisheries, and, to a lesser extent, municipal and industrial water.

6 Salmon of the Columbia Basin (All 5, except pink. Plus steelhead) Chinook salmon (Oncorhynchus tshawytscha ) Coho salmon (Oncorhynchus kisutch) Chum salmon (Oncorhynchus keta) Sockeye salmon (Oncorhynchus nerka) Steelhead (Oncorhynchus mykiss)

7 The major threats to salmon were/are: Harvest Habitat degradation Hydropower Hatcheries

8 Prior to European settlement, the Columbia River produced some of the largest salmon runs in the world: million adult salmon from 200 distinct stocks returned to the river annually.

9 European settlement of the Columbia River Basin 1805 Lewis and Clark reach Columbia River Basin Commercial logging begins in the Pacific Northwest There are 37 sawmills operating in the Pacific Northwest First railroad constructed in proximity to the Columbia River First large-scale irrigation project in the Columbia Basin Commercial fishing industry begins with packing of salted salmon on the Columbia River First salmon cannery is begun 50 miles upstream of the mouth of the Columbia

10 This graph indicates how many pounds of salmon were harvested in the Columbia River Basin through time.

11 Harvest and Columbia River Salmon Harvest was the first activity to depress salmon. The commercial fishing industry captured so many fish that there were not enough adult salmon reaching the spawning grounds to produce the next generation to be harvested. Predictable timing and location of runs made them easy to capture in large numbers using nets, traps, and fish wheels that scooped up salmon and dropped them in a holding compartment). During the first few decades of fishery, fisherman often captured more salmon than canneries could process. Unprocessed fish were thrown back Cannery dock workers. Photo of the collection baskets of a fish wheel. Early warnings did not prevent crisis. Short-term economic benefits were given precedence over long-term conservation; harvest restrictions were weak and poorly enforced, and, at the time, knowledge of salmon biology was limited.

12 Habitat Degradation and Columbia River Salmon Human land-use activities have dramatically degraded the freshwater habitats. Many runs travel hundreds of km (over several weeks or months) to migrate between freshwater reproductive habitats and the ocean. About half of the best spawning and rearing habitat had been lost or severely degraded by 1932.

13 Habitat Degradation and Columbia River Salmon Salmon require cold, clean water. Physiology controlled by temperature Human land-use has reduced the amount of riparian vegetation and cover, resulting in water temperatures being more than 2 C higher than historical levels. Elevated temperatures affect fish directly through influences on metabolism and indirectly through food web changes. Juvenile fish also require shelter (wood in water, foliage on banks )

14 Hydropower and Columbia River Salmon Harvest and habitat degradation had already depressed Columbia River Basin salmon populations by the time the hydropower system was developed in tributaries in the late 19th century. Today there are 14 mainstem dams on the Columbia and Snake Rivers. Basin-wide, there are 400 dams used for hydropower and/or irrigation. The construction and operation of dams has: 1. Drastically reduced the amount of spawning habitat via barriers. 2. Changed flow conditions. 3. Altered habitats in many reaches.

15 Today, 55% of historic spawning and rearing habitats are blocked or inundated by dams. Grand Coulee Dam Hells Canyon Dam MAP OF MAJOR DAMS IN THE BASIN MAP OF AREA BLOCKED BY DAMS

16 Hatcheries and Columbia River Salmon Considered primary means of mitigating the reduction in salmon (and an alternative to other means of conservation, such as harvest restrictions and habitat restoration). Although hatcheries are capable of releasing large numbers of juvenile salmon (approximately 200 million salmon are released into the Columbia Basin each year), evidence suggests that hatchery fish do not perform as well in the natural environment as wild fish. In recent decades, 80% of adult salmon returning to the river were hatched and reared in hatcheries. Even so, the hatchery program has failed to achieve the goals of mitigating habitat loss and degradation.

17 Hatcheries and Columbia River Salmon Hatchery produced fish have negatively affected salmon recovery in three ways: 1. Artificial production has taken resources away from other recovery efforts. 2. Artificial production leads to competition for food and habitat between wild and hatchery fish, particularly damaging if the hatchery fish are unlikely to survive to return and contribute to reproduction as adults. There are now a number of studies showing reduced performance for hatchery-origin fish relative to wild fish in most comparisons 3. Direct genetic effects can occur when hatchery fish breed with wild fish. Studies have shown that the offspring produced by these matings usually have greater mortality and lower reproductive success relative to purely wild offspring. Also, loss of genetic diversity

18 Back to Ludwig et al How can we avoid this pattern of repeated over-exploitation? Ludwig et al. argue we ought to manage Humans, not the resources after all, larger/more immediate the gain, the greater the power, and the greater the probability of over-exploitation (gold rush analogy) Ludwig et al s Principles: 1. Study/manage human motivation (shortsightedness & greed) 2. Act before scientific consensus is achieved 3. Expect scientists to identify problems, not remedy them (by themselves) 4. Distrust claims of sustainability (history repeats itself, ambiguity, & realistic [6 billion people!]) 5. Confront uncertainty and include it in management plans Ludwig et al. 1993