Overview of Marlborough's Ecology and Indigenous Biodiversity
Marlborough, like the rest of the country, has been quite highly modified from the type of natural environment that would have existed for millions of years prior to human arrival less than 1,000 years ago. Much of the land, particularly lowland areas, was cleared of forest or wetland vegetation to make way for new land uses. Many bird species once common to most of New Zealand are now extinct in Marlborough (moa species, kiwi, kakapo) and many more still common bird species like tui, bellbird and kereru are under threat due to limited habitat in some areas. Many introduced pest species of both plant and animal do well in Marlborough, particularly pigs and goats. About 90% of wetland environments have disappeared.
The Marlborough environment is almost two distinct areas in relation to ecology and biodiversity. The Wairau River is the approximate divider between the drier, less forested south Marlborough area (about 700 000.00 ha) and the wetter more forested north Marlborough and Sounds area (about 250 000.00 ha). Together, these areas form a distinctive part of New Zealand's natural environment. The diversity of the region in terms of climate, geology, topography, and its central location, mean that a huge variety of plants and animals occur here, a number at their southern or northern limits of distribution. Click here for MAP.
South Marlborough
In south Marlborough, the dry climate and greywacke and other largely sedimentary rock types have created a wide diversity of habitats, reflected in the character of the native vegetation. The region includes many of the species that make up the mixed forests (beech, podocarps and broadleaved trees), shrublands (including "grey scrub") and grasslands (silver tussock and snow tussock) widespread throughout New Zealand. By virtue of its central location in terms of latitude, the area has species near the southern limits of their range (particularly lowland forest species like rangiora) and some northern limits. The extreme dryness means that plants adapted to those conditions are prevalent. Interwoven into all this is the unique endemic element, including species that have evolved in the special conditions, such as the pink brooms, NZ lilac and Marlborough rock daisy. The widespread occurrence of dry rocky lowland habitats seems to be the key factor for most of the distinctive local species. The native fauna follows this pattern too, and the combination makes South Marlborough one of the genetic diversity centres of New Zealand. In the lowland parts of south Marlborough, widespread historical land clearance and minimal public conservation land means that private land owners have an important role in managing remaining areas with ecological and biodiversity values.
A report providing a summary of the results of the ecology and biodiversity of South Marlborough resulting from a combination of the Council's Significant Natural Areas Survey and the Department of Conservation's Protected Natural Areas survey of private land is available from the Council. Contact Nicky Eade or Ian Shapcott.
North Marlborough - The Sounds
In the Marlborough Sounds a moister climate and metamorphosed schist geology combine with steep topography and complex coastline to create a further variety of habitats and ecological communities. This includes broad leaved forest in gullies, black beech forest on headlands and lowland spurs, hard, red and silver beech occurring on lower to higher slopes respectively, and podocarp species like totara, rimu, matai and kahikatea in the heads of bays and on the lower slopes, although many of these were logged for timber. A significant amount of original forest cover remains, and about half of the land area north of the Wairau River is in conservation estate under the management of the Department of Conservation. Regeneration of land once cleared for pastoral farming is common over large areas, with vigorous native shrublands including manuka, kanuka, tauhinu and broadleaf species establishing. The ultramafic mineral belt which runs through parts of the Sounds supports some distinctive vegetation and a number of rare or unusual plants are found. The area also has important habitat for both freshwater and coastal fish and other species.
The Department of Conservation has a strong presence in the Sounds and a number of the islands like Maud and the Chetwodes, are used for conservation projects to protect endangered bird and animal species. Iwi groups are also involved in conservation work. A number of private landowners are carrying out significant conservation projects as well, often linking the potential for eco tourism and conservation.
Wetlands
Wetlands are highly productive environments that can support a diverse range of plants and animals (birds, fish and insects). Wetlands support processes which provide environmental services like water storage and flood control, nutrient removal, erosion control and water table maintenance. Wetland areas have always been highly valued by Maori providing a rich source of traditional resources like food (fish and birds), flax and medicinal plants.
Most of New Zealand's wetlands were drained between 1920 and 1980 for pastoral land use. They have been reduced by about 85%, and many remaining wetland areas are still under pressure from land development. Of those that are left, many are small and their natural character and habitat quality are degraded by partial drainage, damage by farm animals and weed invasion. Lowland wetlands have been mostly affected and are still at risk in some cases.
In Marlborough an inventory of remaining wetlands was carried out in 2001, to provide an overview of freshwater wetlands and an assessment of their extent, type and the threats they face. (Report available on request).
A brochure describing types of wetland in Marlborough and methods of protecting and restoring wetlands is available from the Council.
Wetland Restoration Brochure (1,179kb)
Freshwater Ecology
The Marlborough region includes a variety of freshwater environments including wetlands, rivers and streams. The main river catchments include the Awatere, the Wairau and the Pelorus.
Numerous other smaller waterways and streams are also present, especially in the Marlborough Sounds, and some of these are still in a very natural state and provide habitat for a good range of native fish, including species like the banded and shortjaw kokopu, red finned bully and long fin eels.
A feature of the dryer south Marlborough area is the many "ephemeral" water ways - those that are seasonally dry for part of the year.
Overall about 19 species of native fish are found in Marlborough's waterways, (there are 35 species found in New Zealand overall), the most common being inanga, common bully and eels. Other introduced species, for instance trout and salmon, are also found in some local rivers.
Aquatic macroinvertebrates (small animals with no backbone, that can be seen by the human eye) are also an important part of the freshwater ecosystem. They are an important source of food for fish and also feed on plant and algae material within the system.
An identification book "Marlborough's Freshwater Flora and Fauna - a Field Guide" is available through the Council - cost $10.00.
Urban Ecology
While urban areas are generally highly modified there are opportunities to look after natural features like waterways, and to increase the habitat for native birds and insects by planting suitable species in both public areas and private gardens.
Marlborough's main urban centres - Blenheim, Picton and Havelock - all have important rivers and streams running through them. They are also located on, or close to, ecologically important coastal areas, including the Havelock estuary, the Wairau Lagoons and the Picton harbour area.
Efforts by the Council to improve the ecology of urban areas include native plantings along the Taylor River Reserve in Blenheim, and more sensitive management of the clearance of vegetation from the water (so that eels, koura and other fish have a better chance of survival), the MacKenzie Street "drain" enhancement in Blenheim, and the increasingly ecological approach to the management of Victoria Domain adjacent to Picton.
Biosecurity
Pests and weeds probably present the largest threat to the remaining ecological values and habitats in New Zealand. A number of animal and plant pests threaten native biodiversity and ecology in Marlborough. The central location and varied climate and landscapes of the region provide a range of habitats and conditions suitable for pests and weeds.
The Regional Pest Management Strategy for Marlborough sets out 32 species of plant and animal classified as pests under some sort of control or surveillance management. Some of these are managed to protect agricultural values (for instance Nassella Tussock and Chilean Needlegrass), and others for purely ecological reasons (for instance Madeira Vine and Boneseed in the Marlborough Sounds - a joint initiative between the Council and the Department of Conservation). Other pest species, for instance the possum, threaten both productive and natural values.
Pest management in the Strategy varies from "total control", where eradication is the long term goal, to "containment control", where the goal is to prevent further spread, and "surveillance" pests where no control is carried out but monitoring and research may occur.
Some pests of ecological significance are included in all three of the above control regimes set out in the Strategy. However there are many where little or no control is carried out. It is likely that future control will be targeted to areas and sites with high ecological values, where pest and weed control will be effective in protecting those values.
Click HERE to view the Regional Pest Management Strategy and other Biosecurity related information.
