My guess is that the second most important threat to the seabirds of the northern North Pacific is the presence of introduced predators, especially foxes and rats, at the breeding colonies. Much of the damage inflicted by these predators may already have been done, but I think their continuing presence is likely to have as great a negative effect on the bird populations as anything else discussed at the conference.
The relative importance of the other identifiable threats to the birds is even more conjectural. Drowning of diving birds in fishnets is obviously of great potential impact, but its importance depends greatly on the rapidly changing practices of fishermen. This problem must be kept under close surveillance, and the establishment and enforcement of international agreements will be critical.
Mineral development has not been mentioned much. It is my understanding that there are prospects for substantial onshore, and perhaps offshore, developments of heavy metal minerals. These are likely to lead to local disturbance in the coastal zone, and the tailings in particular may well pose a threat to coastal and inshore birds.
Ocean dumping has not been mentioned. I do not expect that there will be much dumping of toxic chemicals from Alaskan industries, but we must remember that this area is downstream from Japan and the Soviet Union. I do not know the current practices of these countries, but the unregulated dumping of toxic substances from some European countries apparently has led to large-scale pollution problems in the North Atlantic.
On present evidence, persistent pesticides and polychlorinated biphenyls (PCB's) do not seem to pose a significant threat to north Pacific seabirds, although high levels of PCB's have been reported in shearwaters off the California coast. In my judgment, we have probably turned the corner in regulating these chemicals, at least in the northern hemisphere, and their impact will probably not be allowed to get worse.
Human disturbance is obviously going to get very much worse, both from the influx of new human populations who will be involved in more industrialized activities in Alaska and from the likely increase in tourism. A matter of particular concern is the prospective influx of natural history tours, which can have major adverse effects if not carefully regulated.
Finally, we should not forget the impact of natural phenomena, including climatic changes and vulcanism. Bearing in mind the experience of Katmai, we might expect a natural disaster to strike a major bird colony at any moment.
Practicability of Conservation
Experience from other countries, as related in various papers at this conference, has shown that conservation of seabirds is possible and practicable, even in remote and inaccessible areas. We have heard today particularly about conservation programs and achievements in Europe and New Zealand. W. H. Drury spoke briefly about experience in eastern North America and F. Salomonsen told us how the bird populations of the Faeroes Islands have been managed for sustained yield.
At least in the North Atlantic, where the history of the bird populations is much better known, the conservation situation has been, and probably still is, very much worse than that now prevailing in the North Pacific. Looking back on 200 years in the North Atlantic, we find that two major marine species have been extinguished, at least one and probably two or three others became endangered, and almost all the seabirds were drastically reduced in numbers (at least in temperate latitudes). Starting in the late 19th century when many species first received effective protection, most showed impressive recoveries, but some have declined again in the last 30 years.