Marine Sanctuary study reveals harvesting has low impact on kelp canopy, but more research may be needed.Kelp harvesting off the coast of California by harvesting companies like the San Diego-based Kelco Corp. has been a flourishing industry since at least 1913, when the first harvesting records were kept. Consumer demand for abalone and for products such as ice cream, toothpaste and salad dressing, all of which use kelp, continue to fuel the industry.
What effect has 76 years of consumer demand for kelp-related products had on the giant kelp forests of Monterey Bay? In order to answer at least part of that question, the Monterey Bay National Marine Sanctuary recently conducted a study of the effects of hand-harvesting giant kelp forests off the shores of Monterey and Pacific Grove in what is called kelp bed 220. The study used aerial photographs dating to 1976 and kelp harvest records to examine the real effect harvesting has had on our area''s giant kelp canopies.
The study''s results, released on March 17 of this year, show that kelp harvesting has had no statistically significant effects on the surface canopy of the local kelp.
"The way harvesting is done has low impact on the kelp and little on the associated animals," says Mike Foster, professor at the Moss Landing Marine Lab who did the statistical analysis.
The study has been presented to the cities of Pacific Grove and Monterey, and the Sanctuary''s research advisory committee. "Everyone decided that this isn''t a kelp issue, it''s a user issue," says Foster. "Those folks objecting to the harvesting don''t want the harvesters there because of the image. Kayakers don''t want somebody else using the kelp."
However, some experts say the Sanctuary-sponsored study was not comprehensive enough. For instance, it did not take into account the effects that harvesting has on the ecosystem as a whole, only on the health of the kelp canopies themselves.
"The results are not totally conclusive, but I think that that question is a dead end," says Aaron King, a marine scientist at the Monterey Bay Marine Sanctuary. "Let''s focus on another question: the ecosystem. I don''t know with a lot of certainty if [kelp harvesting] is a factor [in the declining health of the kelp forest ecosystem.]"
"I think it has no important effects at all on the ecosystem," says Foster, "because what is used in the area for harvesting is less than 10 percent [of the kelp forest]."
But Foster admits that a low sample size was used in the study, and recommends that further study be conducted.