By Bob Ferris
With every complicated, science-based issue we seem to tackle, from climate change to wolves and from forestry to diesel particulates, there seems to be a handful of slide-rule era-educated, contrarian scientists who pull themselves up from the depths of retirement to confuse the issue. These self-proclaimed mavens generally have some credentials, but not the applicable ones and they tend to be motivated more by self-interests and politics than by science. And the suction dredging issue is no exception (please see comments section for Suction Dredging…Sucks
Sure, they will be fairly careful in their statements and have the skills necessary to “cherry pick” and present information in a manner that sounds convincing to the lay public, but at the end of the day their arguments are mainly logic wrapped around a kernel of deception. Here are a few of the myths they try to promulgate and why we all should look deeper for the rest of the story. See how many of these myths you can spot in the suction dredging comments.
The steelhead runs after Mount Saint Helens broke records
. Steelhead are anadromous fish (i.e., breed in freshwater and grow in the ocean) and were at sea when the volcano erupted. In any case, the success of that record run was determined 3-4 years beforehand by reproductive success in the rivers and streams. It is not an argument that fish are not affected by silt. (Please see, e.g., Peter A. Bisson, Charles M. Crisafulli, Brian R. Fransen, Robert E. Lucas, and Charles P. Hawkins, Ecological Responses to the 1980 Eruption of Mount St. Helens
, 173 (Springer 2005).
Turbidity does not harm fish
. While it is fun to use the word turbidity, that is really not the issue—siltation is. Turbidity—the opaqueness of water associated with suspended particles—can be a minor problem at the wrong time, but siltation (when those particles settle and where) is nearly always a problem. (Please see California Dept. of Fish & Game, Suction Dredge Permitting Program Literature Review
(2009) at 4.3-22.)
Invertebrate populations rebound quickly after disruption, so it is not a problem
. Young salmon, steelhead, and other fish require invertebrates for food. Steelhead fry (young fish) are also territorial and defend territories; so they also need those invertebrates in their territory. If food resources are locally damaged for any length of time, that can have detrimental impacts on fry. And if these young fish have to move to find food, they also become more vulnerable to predation by other fish and birds. (Please see California Dept. of Fish & Game, Suction Dredge Permitting Program Literature Review
(2009) at 4.3-10, 4.3-16.)
Suction dredgers are good at removing mercury contamination
. Studies indicate that this not an accurate statement. These studies indicate that suction dredging resuspends sequestered mercury and that discharges from dredges in mercury contaminated areas exceeded legal limits by some 10-fold (see page 8 of the following report
Suction dredging damage mimics annual storm disruption. This is not true on two fronts. First and most importantly, the timing is off. Aquatic species in streams and rivers co-evolved with river systems that ran wild during the wetter months and were calm during summer and early fall. If you alter that pattern, impacts to species whose life cycles have evolved in that system occur.
There is also the argument that materials moved are not much relative to the amount of materials moved in association with storm events during the wet seasons for the entire watershed. In fact, one analysis in California showed that the percentage of materials moved by suction dredging was 0.7 % of that moved by the river naturally. That is a crafty but disingenuous argument because natural movement is spread throughout the watershed and suction dredging is localized and intense. In other words, suction dredging may very well not cause much damage relative to total materials moved, but relative to what a particular locale normally experiences, the change can be profound. This same argument can be made for cyclones (i.e., that they are relatively insignificant to annual winds), but I suspect that the person whose house no longer exists sees the situation very differently.
We clean up gravels and improve spawning areas. This statement is misleading as several studies have looked at the impact of suction dredge tailings. And two things become apparent from these studies. One is that fish tend to not use these tailings when natural spawning habitat is also available. The second is that when fish used these tailings and the river flows are high, spawning success is reduced (i.e., fertilized and developing eggs are destroyed) because of the instability of tailings as spawning grounds. (See California Dept. of Fish & Game, Suction Dredge Permitting Program Literature Review
(2009) at 4.1-4, 4.1-8, 4.3-2)
Average California Suction Dredger Gold Recovered
One miner X 35 days per year X $16-$122/per day = $560 to $4,270 per year in gold
Average California Suction Dredger Expenses
General Expenses per miner = $6,250/year
Fuel and Dredge Maintenance = $3,000/year
Average Dredge Cost per Miner (average dredge cost $6,000, assume 10-year life) = $ 600/year
Total expenses per average miner = $9,850/year
Crunching these numbers a little more, we see that the total economic activity generated by suction dredging in California came in at about $15-$36 million for everything (e.g., dredge sales, motels, gold recovered, etc.). While this seems like significant revenue, this pales in comparison to recreational fishing which is a $2 billion plus industry embedded in the $2 trillion California economy.
This is certainly not the economic engine that proponents argue, and California was absolutely their best case scenario. Moreover, it is not appropriate to characterize all of this as potentially lost economic activity, as this sector of the public will likely shift their expenditures to other similar recreational endeavors.
When dealing with endangered and declining aquatic species found in public waterways and surrounded by public lands, we fully agree with Dr. Peter B. Moyle’s view (please see http://www.klamathriver.org/Documents/Peter-Moyle-Expert-Report-on-Suction-Dredging-on-Klamath.pdf
) that the burden absolutely needs to be on the suction dredging industry to demonstrate through independent science that they will not harm these species, either directly or indirectly. Instead, the industry’s strategy has been to malign dedicated experts, discount evidence as rumor, and attempt to confuse the public on the science. I suppose it is much easier and more profitable to sell dreams of riches to the vulnerable members of society, than it is to deal with reality and science.
And please read: