Some of these compounds, like organochlorines, are highly volatile and can travel thousands of miles in air as well as accumulating up food chains so that they have been found in the fat of polar bears at levels which are suspected of disrupting their reproduction. The science of endocrine disruption is still in its infancy with no agreed test for the effect and with many of the findings still tentative. Most natural habitat for New Zealand's indigenous species has been destroyed already by forest clearance, wetlands drainage, and introduction of exotic species. Some farmers have contributed to the latter by releasing goats, deer and pigs into the bush when they were no longer profitable or in order to hunt them. The rate of change since then has not been measured.
Loss of biodiversity is a one way street.
Small areas of ecologically valuable forest, dunes or wetland exist on farms throughout the country. They are diminishing daily in both number and extent, and under the Resource Management Act protecting them is a matter of national importance. However recently the outcry when councils try to set rules for vegetation clearance has led to demands that Parliament substantially weaken the Act and that councils replace rules with voluntary guidelines in their plans. Against this background the farmers who are replanting and fencing off stream banks, controlling predators of native birds, and responsibly keeping their cattle out of forest remnants will not stem the tide of vanishing biodiversity and we will continue to see death by a thousand cuts of our indigenous species. There can be no doubt that environmental quality has been seriously compromised by agricultural and horticultural land use.