8. Indigenous Biodiversity Volume One of non-indigenous species, which have in their own right made a significant contribution to amenity values in both urban and rural environments as well as to the character and economy of Marlborough. This is recognised in other chapters of the MEP. However, it is important to acknowledge that the remaining areas of indigenous biodiversity still contribute significantly to Marlborough’s heritage values. Issue 8A – A reduction in the extent and condition of indigenous biodiversity in Marlborough. Despite the original diversity and uniqueness of Marlborough’s biodiversity and natural areas, human activities have been particularly severe on Marlborough’s sensitive landscape and ecosystems, especially in the terrestrial and freshwater ecosystems of lowland south Marlborough. A continuation of past trends will result in further loss of or deterioration in the condition of Marlborough’s indigenous biological heritage. For Marlborough’s tangata whenua iwi, this will impact on the mauri of natural resources. Terrestrial and freshwater environments Centuries of fire have created the present pattern of small, isolated remnants of natural vegetation. The dry climate and easy contours of most of this land have meant that fires were very effective in clearing vegetation. Very few original areas of native forest remain in south Marlborough – most are secondary vegetation that has regenerated after the earliest fires. Further intensive clearance of shrub and tussock subsequently removed most of the remaining vegetation. North Marlborough has a moister climate and steeper terrain than south Marlborough and has been less modified by human arrival. A significant amount of original forest cover remains and vigorous native regeneration is well underway on land that was cleared for pastoral farming from 1850 to 1940. High populations of exotic wild animals and introduced plants have become well established in Marlborough because of the favourable climate, terrain and land-use. These introduced species have added further pressure on natural habitats. As a result of habitat loss and competition and predation from introduced animals, the original indigenous animals have also largely disappeared; only a few of these species remain in isolated remnant habitats. These habitats are often too small and too far from other sites in the locality to support significant and sustainable populations of native species, including birds, invertebrates and lizards. The ecology of ground water is a relatively new area of investigation. Aquifers are now known to provide a habitat that can support a subterranean ecosystem. Species of crustaceans have adapted and evolved to live and complete their entire lifecycle underground. It is possible that these species may have a role in maintaining underground water quality. To date, little is known of the distribution of densities or even what species are present in our groundwater aquifers. Many of the small streams and waterways on the Wairau Plain, including the largest river in Marlborough, the Wairau River, have been straightened, diverted and channelled over the last 150 years in order to control flooding and enable increased agricultural production. Native riparian or riverside vegetation has been largely replaced by exotic willows and shrubs. These modifications have resulted in the loss of native fish species that rely on native invertebrates falling onto the water for food. With intensification of lowland land-use, particularly for viticulture, the demand for water for irrigation purposes has been significant. In the naturally dry landscape of these lowland areas, taking or diverting water from surface and groundwater sources can result in the loss of habitat as headwaters of spring-fed streams recede or waterways dry up altogether. The increasing use of dams to capture and store water also has the potential to have both negative (e.g. preventing fish passage) and positive effects (e.g. creation of new habitat) on natural areas and biodiversity. 8 – 2