What effects do different land-uses have on the biodiversity of our lowland springs?
Science Centres: Aquatic Biodiversity and Biosecurity
Spring habitats are at the interface of three very distinct ecosystems – groundwaters, surface waters, and land – and the diversity of organisms we find in them often reflects this interaction. For example, we often find multiple species of amphipods in single spring habitats, ranging from darkly pigmented surface-stream forms (top) to unpigmented and eyeless groundwater forms (bottom).
Springs often go unnoticed, yet they are everywhere, and form an important part of lowland landscapes wherever groundwater comes to the surface. They are rich in biodiversity, occurring at the interface between groundwaters, surface waters, and the land, and often contain species from all three environments.
There have been very few studies on New Zealand’s springs, and until recently there was no information on their significant biodiversity values. The Department of Conservation is currently funding a NIWA research programme on the biodiversity values of our lowland springs to try to fill this knowledge gap.
People often think of lowland agricultural areas as highly modified landscapes, dominated by plant and animal monocultures, with perhaps a few native species remaining as relicts (e.g., cabbage trees). However, aquatic habitats within these landscapes can contain many native fish and invertebrate species, which deserve special recognition and protection.
NIWA, through the National Centre for Aquatic Biodiversity & Biosecurity, is helping to identify human threats to our lowland spring habitats. As part of this work we recently completed a survey of the biodiversity values associated with springs in dairy areas in Waikato, Taranaki, Waitaki Valley, and Southland. In 2000, Fonterra Research Centre in Palmerston North set up model catchments in each of these regions to study the environmental effects of dairying, and our studies on spring biodiversity are contributing to this programme.
We sampled 34 lowland springs and seepages during the survey in January 2003, and collected 113 invertebrate species. Many of these species had not been named scientifically, in particular, a large number of amphipod species that included 13 distinct forms of Paraleptamphopus. We also found three new species of hydrobiid snails in springs from limestone outcrops in Southland’s central plains.
Our results indicate that the condition of riparian vegetation around springs is an important factor determining the makeup of invertebrate communities. Several invertebrate species (e.g., the mayfly Zephlebia nebulosa) were found only where springs were completely shaded by native vegetation.
We were also interested in the threats posed to spring fauna from stock access. However, we found that springs with full stock access did not always have low biodiversity. For example, in one small spring with full stock access we found two of the three new species of snail. Our results, and overseas studies, suggest that stock may pose less of a threat to biodiversity values in springs than land managers, who have the potential to seriously affect spring habitats through drainage and land clearance.
We will continue to develop a better understanding of the biodiversity of spring habitats in lowland areas over the next 2 years, and will provide the knowledge required to ensure more effective management and protection of these important habitats.