WHO GOES INTO THE ARK?

Forest and Bird, Volume 23, Issue 2, 1 May 1992, Page 38

WHO GOES INTO THE ARK?

and

ALISON

MARK BELLINGHAM

JANICE MOLLOY

how to decide which species are the most threatened

The dilemma faced by all conservation managers and scientists is how to set priorities for different threatened species. How threatened is each species? When do we have to act to save a species? How much of the limited conservation budget should go into a particular species

as opposed to another?

look at

some recent advances.

N THE PAST, species conservation in New Zealand has concentrated on birds and some reptiles, with some work on plants and the occasional marine mammal and invertebrate. There has been no systematic way of working out which conservation work should have priority. One of the main factors in determining priorities has been the interests and expertise of scientists and managers rather than the needs of threatened species. There has been extensive work, for example, on the Cook Strait and northern tuatara populations which each number more than 50,000 animals. Scientific interest in this species is high but should this interest dictate our conservation priorities especially when their population is far larger than that of the Chatham Island oystercatcher or the Mokohinau skink? More recently, the Department of Conservation, which has primary responsibility for protecting native plants and animals, has made a conscious effort to work on a wider range of species. However, this has been difficult given that the expertise of DoC staff has remained based on particular groups such as birds and some reptiles. Another problem is that once you have identified the species under threat which ones do you work on? In the Northland conservancy, for example, there are more than 40 endangered species, many endemic to the region, while there are few threatened species in Hawke’s Bay. There was an obvious need for a method to identify the priorities for species conservation and the factors affecting the survival of those species. In the past two years DoC has helped develop a more systematic approach. This has evolved into the Species Priority Ranking System (SPRS) which is applied to indigenous vascular plants, terrestrial insects, spiders, land snails, amphibians, reptiles, birds, bats, marine mammals and a separate list of plants important to Maori. At present it excludes other marine fauna, other invertebrates and non-vascular plants (mosses, liverworts and algae). The SPRS was developed along the lines of existing US, Australian and World Conservation Union species ranking systems. Most of these use a number of common criteria based on taxonomy, threat of extinction and natural and cultural values. This was refined so the system could be used to compare New Zealand ferns with fish, or penguins with palms rather than the traditional approach of only comparing species within a group, such as different species of birds. The criteria used in the SPRS are:

* taxonomic distinctiveness: i.e. the absence of close relatives * population features: number of populations, mean population size, largest population, distribution, condition of largest population, decline of wild populations ¢ vulnerability: whether a habitat is under legal protection, the extent of habitat loss, the impact of predators and harvest, competition, habitat or diets specific to that species, reproductive and behavioural specialisations * potential for recovery through propagation or protection away from the species’ natural habitat * cultural value to both pakeha and Maori The species were grouped into taxa, which are taxonomic units that include both species and subspecies. Taxa were scored against each of the criteria and, rather than ranked linearly, were assigned to three categories of urgency. Category A are the threatened taxa requiring urgent recovery work to prevent possible extinction. Category B are those taxa requiring recovery work in the short term and category C are those requiring recovery work in the medium term. HE PRINCIPAL REASON for developing the ranking system, was to aid DoC in setting species conservation priorities, and to identify taxa needing urgent recovery and protection work. Since the ranking system has been developed there has been better targetting of funds, a process helped by the formation of the Threatened Species Unit of DoC which co-ordinates this work. In developing the ranking system we accumulated a considerable amount of information on New Zealand plants and animals. This has enabled us to build up conservation profiles of 284 plants and animals (85 in category A and 199 in categories B and C). These profiles were previously not available for most species, particularly insects. The profiles will be extremely useful for managers and conservationists working on threatened species as they give information on the state of a population and pinpoint the main factors affecting its survival. Figure 1 shows the proportion of threatened taxa within each group. Using the groups covered by the SPRS the estimate of the total biota of New Zealand is 23,000 taxa, of which 20,000 are insects. 284 of these taxa are endangered and vulnerable. There is some justification for the concentration on bird protection and

Figure 1: New Zealand taxa covered by the Species Priority Ranking System.

* WHO GOES INTO THE ARK?*

recovery programmes with just under half of the bird fauna endangered or vulnerable. Reptiles and freshwater fish groups also have a high percentage of threatened taxa while only five percent of all plants are threatened. All of New Zealand’s frogs and bats are threatened. The small proportion of threatened insects probably reflects a lack of knowledge of this group. The level of taxonomic distinctiveness of individual taxa is important in deciding where to put the conservation effort. If protection and maintenance of biodiversity is the goal we should be saving taxa with the highest level of taxonomic distinctiveness before those less distinct taxa. In other words a plant which is the only member of its genus has a greater priority than one which is one of 20 species in the same genus. Our analysis showed that birds, followed by plants, have the highest number of taxa that are taxonomically distinct. Again this may well justify the disproportionate conservation efforts on birds in New Zealand. Birds, being at the top of the food chain, are also good indicators of ecosystem health. N NOTHER GOAL of the SPRS is to identify major threats to taxa » and how these threats might differ 4. +» between groups. When we looked at threats of predation, competition and habitat loss on these taxa it is clear how much of a future problem exists to control and eliminate predators. The analysis shows that predation and competition are the main factors that seriously threaten the survival of New Zealand plants and animals. Almost half of the category A taxa are affected in this way. It may seem surprising that habitat loss is less important but this is because 70 percent of threatened taxa are in habitats where we expect negligible change in the next ten years. While habitat loss has been a major cause in the past of the depletion and extinction of many populations, natural areas are now more secure with a large slice of New Zealand administered by DoC. However, the SPRS does not identify whether a plant or animal has sufficient stable habitat to survive in the long-term. All the taxa seriously affected by habitat loss are plants. Predation is affecting the survival of a considerable proportion of mammals, freshwater fish, reptiles/amphibians and land snails, while competition is having its biggest effect on mammals and plants. The major factors are introduced animals (possums, rats, trout, deer, goats) and weeds, and the impacts of the fishing and farming industries. ey ss of .

Loss of habitat is often irreversible, particularly in the short-term, and the prevention of habitat loss is often easier than controlling the insidious effects of predation and competition. We identified three threatened habitat types which are declining rapidly that are important for threatened taxa: * coastal herbfields and dunes ¢ freshwater wetlands ¢ lowland shrublands. It is no co-incidence that these habitats are also threatened ecosystems that were severely reduced in historical times. Nine-tenths of New Zealand’s original wetland, for example, has been lost. A high priority will be to prevent any further loss of habitat of the 11 taxa which we expect will have major threats to their habitat in the next ten years. All of these taxa are plants and they are endangered from other factors also. "| HE SPRS can also be used to identify key sites for species and habitat protection. Although habitat may not be declining for a taxa, caine might it be legally protected. We found that ten percent of threatened taxa did not have any legal habitat protection. The highest proportion were freshwater fish, while the highest numbers were plants. In contrast, more than half of our threatened land snails, insects and reptiles/ amphibians have legal protection on most or all of their habitat. Even when habitat sites are legally protected the threatened taxa present can be harmed by predation and competition. Often a protection programme for a species, such as animal or plant pest control, or water level restoration are needed in addition to protection of habitat. Apart from the three declining habitat types listed above, there are other important habitats which have little protection. Marine areas, for example, are critical due to the high number of seabirds. Very few marine areas important for seabirds are protected, and seabirds are not protected beyond 20 kilometres at sea. The habitats most important for threatened plants, namely lowland shrubland, coastal herbfields and freshwater wetlands are the most severely reduced in area and are under-represented in the conservation estate. In contrast, forested habitat of land snails is more abundant and better protected. We also mapped the distribution of endangered and vulnerable taxa to understand any geographical patterns. We expected some concentration of threatened taxa because there are many endemic plants and animals in New Zealand which only occur in one or two areas.

What we found was that a third of threatened taxa — and half of those in category A — have only one population, and are found in very restricted areas. As would be expected, snails, plants and insects have the narrowest geographic range. Only 11 of the taxa (nine of them plants) are also found outside New Zealand in a threatened status. With many threatened taxa having few populations and restricted ranges, our next task was to see if these taxa were concentrated in any of New Zealand’s ecological districts. We found an uneven distribution of threatened species with highest numbers in the Te Paki, Chatham Islands and Cook Strait ecological districts. The high numbers of threatened taxa in some districts have tended to escape the notice of conservation policymakers and managers. This needs to be corrected and it also emphasises the need to target conservation efforts across the country according to national needs first and regional needs second.

Habitat destruction and the introduction of exotic species have influenced present-day patterns of regional biodiversity. Some areas have become refuges for remnant populations. In these areas the distribution of threatened taxa does not always represent a centre of endemism and biodiversity, but rather a history of chance survival of vulnerable species. In order to protect and maintain its biodiversity New Zealand must protect sites that are rich in species and have diverse ecosystems. Where these sites all occur within any one ecological district, such as Te Paki in the far north and the Chatham Islands, these are key areas on which to focus protection efforts.

NOTHER ROLE for the SPRS will be to enable researchers to , identify key areas for the study of ~» threatened species that are likely to attract research funding. DoC and conservation organisations such as Forest and Bird can focus on raising the profile of some endangered but forgotten species and their habitats. The SPRS can also provide a better focus for the various commercial sponsorships for threatened species. Forest and Bird, the New Zealand Conservation Authority and DoC are attracting considerable commercial sponsorships for such species. In the two years it has been operating, the Threatened Species Trust has generated over $2 million for kakapo, kokako and kiwi — all high priority threatened species. Sponsors are more likely to support recovery programmes if their species can be shown to be particularly important and if they can see that the conservation managers have got their priorities worked out with strategies for assisting species in serious decline. OR TOO LONG in New Zealand species and habitat conservation has had no unified identification of threats to species. We now have a process where profiles of threatened species, threat factors and their relative importance can be used to guide conservation efforts. Identification of key taxa and habitats will aid the protection and maintenance of New Zealand’s biodiversity. At the same time this should not detract from efforts to protect the more common species and representative ecosystems and communities that are the backbone of New Zealand’s natural biodiversity. %

Alison Davis has worked on a number of threatened species projects. She is the manager of protected species policy for the Department of Conservation. Mark Bellingham is the field director of Forest and Bird. He has coordinated Forest and Bird’s work on threatened species for the last five years. Janice Molloy is a protected species policy officer at DoC and has coordinated the development of the SPRS.

A technical report on the Species Priority Ranking System is available from DoC’s Head Office, PO Box 10-420, Wellington.

group no. of taxa threatened taxa as a percentage in SPRS of total group reptiles & amphibians 2/ 60 birds 70 42 freshwater fish 22 mammals 16 land snails 51 11 plants 93 5 insects 31 0.2 total 284