RMA AND ENVIRONMENTAL RESEARCH PERSPECTIVES OF THE USE OF SOIL-PLANT SYSTEMS TO MANAGE THE ENVIRONMENT
Selva Selvarajah
Otago Regional Council, Dunedin
From the regional council's perspective the Resource Management Act (RMA) provides greater regulatory control over water quality and quantity management. Air and soil quality management is based on contaminant discharges. The regional councils can also manage land for the purpose of soil conservation. Despite the relative significance to water management, soil-plant systems continue to play a major role in environmental management in New Zealand.
Coupled with cultural needs and relatively higher assimilative capacity, soil-plant systems have led to land being the preferred discharge medium over water. Despite their relatively limited treatment capacity constructed wetlands are also preferred over direct discharges to water. Market access for food products, climatic and soil conditions, land value and sensitive groundwater aquifers are key limiting factors.
Soil-plant systems are also vital in mitigating against non-point source discharges. Riparian strips are known to minimise terrestrial contaminant entry to surface water. A more important role of riparian strips is reducing water temperatures and thus minimising algal proliferation in nutrient enriched surface waters. Regional councils also promote the use of riparian trees to improve stream/river bank stability.
Regional councils have limited control over land use. However, councils can regulate land use for the purpose of soil conservation and water management. Trees and grass cover continue to contribute significantly in minimising soil erosion. Nevertheless, in areas where water recharge is critical to maintain water quantity, restrictions may be imposed on aforestation to reduce water losses. In some regions, land use restrictions may be placed in sensitive catchments where water quality is the major focus.
There has been an increase in the use of soil-plant systems to remedy contaminated sites and rehabilitate mining sites. Whilst rehabilitation of mining sites has been in practice for a long time, phyto-remediation of contaminated sites is relatively new. Where there is migration of contaminants at a contaminated site, management/ownership requires resource consent. In their decision making process the councils will consider the actual and potential risks of a contaminated site and the timeframe within which the contaminant migration is contained or minimised. Where off-site migration is to be dealt with urgently, phyto-remediation has limited use. Such technologies will be useful for long-term clean-up operations.
There are sufficient opportunities for regional councils to conduct/commission their own research or support/rely on public funded research in New Zealand. Depending on the affordability and urgency of the information requirement, councils fund their own research. Some councils conduct collaborative projects with research organisations or fund post-graduate studies. The relative council fund input to scientific research is low compared to their ongoing state of the environment monitoring. A larger proportion of such monitoring is not related to soil-plant system monitoring.