So what are the results of this activity? The thing is, if you mess with nature, the consequences can be quite serious. Let's take a look at a couple of cause and effect situations. San Francisco Bay is prime real estate which means that the large estuary has shrunk by 60 percent with land reclamation, which is now so overrun with alien species it can no longer support commercial fighing. A city sewage plant outside Los Angeles has contributed so much polluted effluent that it replaced a kelp forest with sludge laced with toxins and heavy metals. The point is that estuary and its tides acted as part of Nature's way of dealing with pollution. So did the kelp forest. Get rid of them and you reduce the ocean's ability to do what we wait it to do - disperse wastes and deal with pollution.