A new approach to biodiversity protection: local to landscape scale
Al Glen checking an artificial cover object used for monitoring invertebrates and skink. Image - Wendy Ruoscoe.
Management of invasive pest species is rarely conducted at a landscape scale. More typically, pests are managed intensively in small areas that are deemed to be of high importance, with little or no management undertaken in the surrounding landscape. This helps some native species persist in places where invasive animals are controlled, and individuals may occasionally disperse between protected areas. Such disjunct small sub-populations are known as metapopulations.
Wendy Ruscoe and colleagues have been investigating how concepts from metapopulation theory can be used to improve management for native biodiversity. Conservation groups in New Zealand often focus on preserving, restoring and even re-introducing native species in relatively small areas. An obvious practical means of adopting metapopulation concepts is to use these small protected areas as ‘source’ areas for re-establishing species nearby, or as ‘stepping stones’ that help native species disperse across whole landscapes.
One example of such an approach is the ‘Wide-scale Predator Control Programme’ being undertaken in Maungaharuru-Tutira in Hawke’s Bay. There, pests have been controlled at Boundary Stream Mainland Island (BSMI) for about 15 years. The Bellbird Bush and Opouahi Reserves and many smaller privately owned blocks also provide protected native habitat but are separated from the BSMI by unprotected agricultural land. Populations of native species including kiwi, kōkako, robins, and Hawke’s Bay tree wētā persist in the BSMI but are under threat from invading animal pests. The threat of predation is especially intense when native animals move between these protected areas.
So far, only one pre-control and one post-control monitoring session have been completed (Table 1). Pest monitoring is being undertaken using standard tracking tunnels. Native skinks, wētā and other invertebrates are also recorded using tracking tunnels and other specific devices. These devices include wētā houses and Artificial Cover Objects (ACO’s) for invertebrates and skinks, and were checked for the first time in February 2012 (Table 2).
Bird song is being recorded using experimental devices produced by DOC. These were placed on the bush-pasture margin on a subset on lines in each of the two experimental areas. Bird song recordings were done in 8-hour blocks Table.1 Species recorded by tracking tunnel lines in February 2012 (post-control). (05:30–13:30 and 17:30–01:30) over three days, and the recordings saved onto memory cards. (SD-Secure Digital Flash Memory Card).
Although vertebrate pests are being controlled over a relatively large area, reinvasion is likely to occur. Samples of genetic material are being collected from the carcasses of cats and ferrets trapped within the predator control area to determine where the pests are coming from and hence allow for more targeted control in the future. This technique has been used by Landcare Research and the University of Auckland for mapping possum dispersal in Hawke’s Bay.
The metapopulation approach means that both large and small sites, from small community-led initiatives to large-scale agency-funded pest control operations, have the potential to contribute to the survival of species throughout the landscape, with immigrants from neighbouring areas providing a ‘rescue effect’ whenever necessary. The resilience of this network of sites, or metapopulation, is much greater than that of a species confined to a single, isolated site.
This work is funded by the Ministry of Science and Innovation (Programme CO9X0909 ‘Invasive Mammal Impacts’ Program within the ‘Managing Invasive Weeds, Pests and Diseases Portfolio).
Wendy Ruscoe, Al Glen & Mike Perry
Table.1 Species recorded by tracking tunnel lines in February 2012 (post-control).
Table 2. The number of lines on which each native species was found.
