Biodiversity - what does it mean?

In freshwater ecosystems, loss of indigenous biodiversity is a pervasive environmental issue. Biodiversity in this context means the full expression of the natural components of the ecosystem that were present before widespread habitat modification, harvest of native species, and introduction of exotic species, whether by accidental or intentional means. Species richness, genetic diversity, and unmodified indigenous communities are all components of biodiversity.

Habitat modification has occurred through removal of native forest, intensification of agriculture and horticulture, planting of exotic forests, and dam construction. Harvest of native fish occurs predominantly through the commercial, recreational, and traditional fisheries for eels and whitebait. Introduced exotic species that are now widely distributed in New Zealand are fish such as trout, perch, goldfish, catfish, mosquitofish, rudd, and koi carp. Invasive aquatic weeds such as hornwort and oxygen weeds are also widespread, and displace native aquatic plants in many cases.

The decline in biodiversity is especially hard to reverse in lakes where invasive weeds and invasive fish such as koi carp have out-competed indigenous species. Additionally, invasive fish have altered the physical and biogeochemical environment to produce conditions that favour proliferation of harmful algal blooms. Furthermore, new evidence on land use intensification suggests that there will be large increases in nutrient export from land to water, which will also increase the risk of harmful algal blooms and biodiversity loss as groundwater and stream flow composition equilibrate to the intensive land use. Increased nutrients also tip the balance of habitat suitability in favour of invasive fish.

Our research will help reverse the decline of New Zealand’s freshwater biodiversity by developing (1) sensitive methods to detect early stages of decline resulting from harmful algal blooms, (2) improved methods for invasive fish eradication, and (3) decision support tools for lake management and risk assessment. These technologies will be integrated into a programme of outreach and education on water quality, biodiversity and invasive fish impacts on lake ecosystems. Social and legislative research dimensions and a strong end-user collective will ensure that communities are empowered to take responsibility for biodiversity protection and enhancement, and that designated management authorities overcome impediments related to technology transfer, policy, and planning.