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Press, 7 April 1979, Page 15

By

ELIZABETH MEARES

Two pressing questions of today lack satisfactory solutions: the use of selective herbicides, and the destruction of native bush by feral animals. “With the wild sheep and goats removed,” says an Arapawa Island resident, “introduced weeds will soon get beyond control. Nettles, convolvulus, and other weeds will smother native plants in the reserve.”

On Motunau Island, after the eradication of the rabbit, boxthorn grew unchecked until seabirds could no longer nest there. In energetic competition with native plants introduced weeds flourish. European weeds reach a size and tenacity not known in their home environment, and threaten to overwhelm their hosts. New Zealand bush regenerates rapidly in high rainfall areas.

The bush evolved in uniquely specialised forms through continual heavy grazing, so the total eradication of grazing feral animals may pose a greater threat than does their

presence. Is it possible to restore native bush reserves to their original state without the presence of selected grazing animals? When the first men, an early race of East Polynesian origin, came to New Zealand bringing weapons and fire, giant flightless birds kept the vegetation in check. Enormous numbers of huge wingless birds gobbled and swallowed and trampled their way across the land.

Moas, having no enemies before the coming of predatory man. ranged and grazed in adaptions of variety and size for every type of terrain through the land that was then one island.

Swamp and bog, alpine meadow, sanddune and salt meadow, grasslands and rain forest, all had specialised forms of moa, some reaching 12ft in height. Moas took the place of grazing animals in necessary control of vegetation. History tells little of the first men. Moa-hunters, as they are now called, increased and populated the land. Remains of 22 species of moa have been found in association with man. Diggings such as in Pyramid Valley reveal the astonishing numbers in which the giant birds once existed. Some varieties may have died out naturally, but at the time of the next Polynesian inhabitation many moa species

were extinct. The last moa was killed about the time of Captain Cook’s voyages, and the moa-hunters had become a legend. Into a country of profuse vegetation Captain Cook released goats and sheep. Early settlers brought animals for food and sport. Some, like the rabbit, increased so explosively that small predators were introduced to keep numbers in check.

If New Zealand native flora needs grazing for stable regeneration, the introduction of feral grazing animals was timely, after the loss of the moa, an enormous flightless goose, and other grazing birds. Goat, and sheep that Captain Cook released on Arapawa Island live today as they did for more than two centuries, as an isolated colony away from outside genetic exchange. Ideal conditions prevailed, with no adaptations necessary, so no changes took place within the species. While in England the original .species vanished through domestication and interbreeding.

Today, we see the results of this pocket isolation on Arapawa Island. For more than 200 years the environment supplied their requirements and the grazing animals checked native overgrowth and controlled introduced weeds, perhaps with grazing habits similar to those of the extinct moa.

Are the unique features of Arapawa Island’s native reserve attributable to the presence of the goats? The introduced animals and the bush established a balance that proved of benefit to both. A recent deterioration of the bush spelled doom for the goats, and culling proceeds, but an observer on the Island confirms a scientific report that “Domestic cattle are doing a greater amount of damage than goats.” Cattle have different grazing habits and until recently a herd of 500 grazed the reserve. Evidence can be seen now of the presence of cattle. On Arapawa Island the feral goats and sheep pose a dilemma. Is their presence in the reserve causing damage? Will their removal cause graver deterioration? Much of New Zealand’s vegetation is unknown in the rest of the world. Plant forms evolved side by side with large birds that pruned them severely. Introduced weeds compete with native vegetation. Will selective herbicides take the place of feral grazing animals?