State of Biodiversity in Canterbury

Terrestrial (land)

Canterbury's land-based indigenous biodiversity has experienced considerable decline.

Most of the decline has occurred in the lowland and coastal environments of the region, where around 90% of the previously extensive native plant cover has been lost, and in some areas less than 1% remains. Native forests, shrublands and grasslands in these areas now only occur in small, scattered fragments. But these fragments support a disproportionately high percentage of the region's most seriously threatened species and ecosystems, and it is these that are at the greatest risk of further loss.

In hill country and inland basin areas (between about 400m and 800m elevation), biodiversity losses have not been quite as extensive. Important forest remnants, tussock grasslands, and some key ecological corridors remain. However, in some areas remaining biodiversity is under increasing threat due to rapid land use change and intensification, and the impacts of pests and weeds.

Alpine and high country environments (above 800m elevation) generally remain dominated by indigenous vegetation, with large areas of tussock grasslands, as well as extensive wetland complexes. However, these areas are also subject to increasing pressure from both land use change and the spread of pests and weeds, including an increasing threat from wilding conifers.

Extend of Loss Map

Freshwater

Rivers, streams, lakes and wetlands provide important habitat for many freshwater fish, invertebrate, plant, and bird species. They also act as corridors and 'stepping stones', connecting different habitats and ecosystems.

However, many of these water bodies are affected by what happens on adjacent land. For example, the loss of riparian (bankside) vegetation or development within the wider catchment often has negative impacts on a waterway. The resultant changes in water quantity and quality can have adverse effects on the distribution and lifecycles of many plant and animal species, which have often adapted to the specific physical conditions that were previously present.

Our most degraded waterways are the lowland streams, the lower reaches of braided rivers, and wetlands. As a result of drainage and reclamation, only about 10% of the wetlands of the region remain; in coastal areas this figure is estimated to be only 5%.

In hill and high country areas, water quality has generally remained relatively high, although changes in land use are causing water quality degradation in some rivers, lakes and wetlands.

Coastal and Marine

The Canterbury coast is ecologically diverse and rich in marine life. There is a wide range of marine and coastal ecosystems that support many species, including an abundance of seabirds, marine mammals, diverse fish fauna and seaweeds.

The many river mouths, estuaries and coastal lagoons of the region provide extremely important habitats for large numbers of indigenous plants and animals. These areas have an important function as a link between the freshwater and marine environments. These estuarine and coastal areas also hold significant cultural value for Ngai Tahu.

Canterbury's dune systems are also ecological treasures, providing unique habitats for plants and animals that are specially adapted to living in harsh and changeable coastal conditions.

However, as with terrestrial and freshwater ecosystems, land use, development and increasing demands have impacted considerably on the region's coastal and marine environments. Water and habitat quality in many of our coastal areas have been degraded, many of the coastal forests and shrublands have been cleared, and there has been extensive vegetation loss and habitat modification in our dune environments. Many of the plant species specially adapted to coastal cliff environments are threatened by grazing and pests, and there are increasing pressures and demands on our marine environment through aquaculture and commercial and recreational fishing.

Key Threats to Biodiversity

The losses to our indigenous biodiversity have been due mostly to:

These continue to pose the greatest threats to our remaining biodiversity.

Of these threats, animal and plant pests pose the greatest problem to our remaining native species. Pests prey on, and compete with, our native species, and can introduce disease and hybridisation.

Habitat size is also a critical factor in maintaining native biodiversity. When a habitat is reduced to around 20% of its original size, the rate of biodiversity loss accelerates rapidly, putting remaining species and habitat under increasing threat of further loss. In many parts of Canterbury, remaining indigenous habitat is well under this critical 20% threshold.