biodiversity

Biodiversity assets often require conservation management, which, in turn, necessitates decisions about which ecosystem, community or species should be prioritised to receive resources. Population viability analysis (PVA) uses a suite of quantitative methods to estimate the likelihood of population decline and extinction for a given species, and can be used to assess a population's status, providing useful information to decision-makers. In New Zealand, a range of taxa have been analysed using the PVA approach, but the scope of its implementation has not previously been reviewed.

In New Zealand, as in other developed nations, community-led conservation groups work to maintain and restore ecosystems and conserve indigenous biodiversity. These groups receive support in the form of materials, technical advice and funding from central and local government and non-governmental organisations, who are required increasingly to demonstrate delivery of benefits or conservation returns on investments. However, there is little empirical evidence for the objective evaluation of the effectiveness of community-based programmes in achieving national conservation outcomes.

The lowland Canterbury Plains of New Zealand have been extensively modified since human occupation, but with recent conversions to irrigated dairy farming very few remnants of native dryland vegetation remain in the region. We investigated soil chemistry, plant distribution and soil invertebrates along transects in Bankside Scientific Reserve, a small (2.6 ha) remnant. The vegetation is a mosaic of native woody shrubs, predominantly Kunzea serotina (kanuka, Myrtaceae) and Discaria toumatou (matagouri, Rhamnaceae), and dry grassland.

More than 600 community environmental groups across New Zealand are engaged in restoring degraded sites and improving and protecting habitat for native species. In the face of ongoing biodiversity declines, resource management agencies are increasing their reliance on these groups to enhance conservation outcomes nationally. However, little is known about community groups and their activities beyond local or regional studies.

Ecological impacts of three weed species of similar life form, Asparagus scandens, Plectranthus ciliatus and Tradescantia fluminensis, were investigated in six lowland forest remnants in New Zealand. All three species form dense, ground-covering mats of vegetation, and are tolerant of a broad range of light environments. Relationships between canopy openness, weed volume, native plant abundance and native species richness were investigated. Volume of all three weed species increased as canopy openness increased.

In most regions of the world removal of environmental stress facilitates regeneration of native plants and habitats. However, in many of New Zealands modified landscapes, exotic species are likely to respond first to any reduction in stress because these fast-growing species are prevalent in local vegetation and dominate seed banks.

The Canterbury Plains have lost most of their pre-Polynesian indigenous vegetation, primarily forest and shrubland. One of the few remaining areas is the 2.3 ha Eyrewell Scientific Reserve which consists mostly of low kānuka (Kunzea ericoides) forest and a small area of grassland. We assessed the Reserve vegetation using a combination of plots and transect surveys at different times of the year between 2001–2003. For comparison with the Reserve vegetation we also assessed plots in an adjacent grazed kānuka remnant, adjacent cultivated pasture and Eyrewell Forest, a pine plantation.

Vegetation was sampled in kahikatea (Dacrycarpus dacrydioides)-dominant forest fragments having different recovery periods since grazing ceased in the Waikato region, North Island, New Zealand. Changes in vegetation were modeled against recovery periods ranging from 0–74 y and in relation to position within fragment (edge or interior). Indigenous plant species richness increased and adventive plant species (mostly pasture herbs) richness declined with increasing recovery period; small tree and sapling density and seedling ground cover increased.

This study examined whether the diversity and relative abundance of ground-dwelling invertebrates changed in relation to type of vegetation cover. Invertebrate taxon diversity and relative abundance were assessed with pitfall traps placed under the native shrubs Olearia bullata and Coprosma propinqua, and in surrounding patches of exotic pasture. A total of 1935 invertebrates and at least 152 invertebrate taxa were recorded from 49 pitfall traps. The number of native taxa was c.63% of all taxa recorded, whereas exotic invertebrates represented only c.9%.

The New Zealand flatworm, Arthurdendyus triangulatus (formerly Artioposthia triangulata) has become established in the British Isles and the Faroe Islands and its human-mediated spread within Northern Ireland and Scotland is well documented. The geographical distributions within New Zealand of it and two related species, A. australis and A. testacea have always been assumed to reflect the natural distribution patterns.