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AN EXPLOSION in the population ofAntarctic fur seals has caused wide-spread changes to many coastal, terrestrial and freshwater ecosystems in thenorthern maritime Antarctic islands andon the

west coast of the AntarcticPeninsula. Dominic A Hodgeson andNadine M Johnston of the BritishAntarctic Survey, Cambridge, conductedstudies based on used seal hairs found inlake sediment

cores from one maritimeAntarctic island as a historical recordof seal populations (Nature, Vol 387,No 6628). This enabled them to study the possible causes of the increasing numbers of

visiting Antarctic fur seals, and has provided a historical framework fromwhich to evaluate conservation plans tominimise the adverse effects of seals atsites of particular ecological

importance. The procedure of examining sediment cores for the presence of seal hairsto evaluate the seal population is quiteaccurate as the evaluation since 1977corresponds to the census

data available.So it can be assumed to safely assess theseal populations for the periods forwhiclif data is unavailable. Though the Antarctic seal washunted to near extinction during

thenineteenth and early twentieth century,their numbers have been increasingrecently. From less than 100 seals thatvisited Signy Island in the South OrkneyIslands from the main breeding

beachesin South Georgia in 1976, their numbershave gone up to almost 20,500 in 1994.This large increase has caused extensivedestruction of vegetation, soil erosionand the eutrophication

(depletion of theoxygen content in a lake due to extraordinary growth in organic and mineralnutrients) of freshwater lakes on coast-lines where the seals haul out.The protocol on environment

protection was adopted by the AntarcticTreaty Nations in 1991 and it is expected to enter into full international forcein the near future. Given the commitment of the Treaty Nations to

limit theadverse effects on Antarctica, the current fur seal population raises threeimportant questions. First, is theincrease the result of human or naturalinfluences? Second, does the

increase fitin the range of normal population variability during the past several thousandyears? Third, how might any controlmeasures that are deemed necessary beimplemented within the

AntarcticTreaty system? As the study of ieal hair found inlake sediment cores from Signy Islandmake it possible to study the timing ofthe Antarctic fur seal population explosion in relation

to possible causal factors. Geophysical and biological palaeoclimate indicators in sediment coresshow that the population explosion isunlikely to have been influenced bychanging natural

ecological conditions.However the evidence does suggest alink between seal populations and theactivities of the whaling industry. A short sediment core showed thatseals visited the island

before commercial sealing began, but declined in numbers during the sealing periods in thenearby South Shetland Islands between1820 and 1870s. As sealers withdrewfrom the South Shetland

Islands thereseemed to be brief increase in the abundance of visiting seals, but regional sealing based in South Georgia continued toreduce the population near to extinction. There is no

evidence that fur sealsvisited Signy Island between 1950 andthe late 1970s, and it was not till 1977that the summer influx of seals began toincrease rapidly. One possible cause ofthis

increase might be the greater than90 per cent reduction in the number ofbaleen whales in the Southern Ocean bythe whaling industry since 1922. Thisseems to have resulted in an abundanceof

the Antarctic krill (on which thewhales feed) which has subsequentlybeen available to seals. The'number of seals hairs presentlybeing deposited in the sediments is 78-94 per cent

greater than at any duringthe past 6,570 years (as measured fromthe radiocarbon system of dating). Thisimplies that the present number of visiting seals exceeds the range of

naturalvariability. At present there is no evidence of any particular species or community type being endangered by theseals, but in the northern maritimeAntarctic islands and on the west

coastof the Antarctic peninsula, changes tolowlands and freshwater ecosystems inthe past two decades is significant andare apparently spreading. There is a growing need for theAntarctic

Treaty Nations to considerhow ecologically important sites mightbe protected. Though this can be doneby preventing the seals from gainingaccess to areas of particular ecological orscientific

importance through themeans of wire mesh and electricalfences, such methods might prove to becontroversial. Besides, they might beunnecessary when regulations set tomanage stocks of whales,

as ascribed inthe International Whaling Commission,and stocks of fish and krill, as governedby the Convention on the Conserptionof Antarctic Marine Living Resources,begin to exert a

regulatory influence onseal populations in the future.