Archived 2011-2012 topics: St Helena Plover (Charadrius sanctaehelenae): downlist to Vulnerable?

Initial deadline for comments: 31 January 2012 [note that this has been moved back by about two months].

BirdLife species factsheet for St Helena Plover

St Helena Plover Charadrius sanctaehelenae is endemic to St Helena (UK), where it inhabits pastureland and semi-desert habitats (McCulloch 1992, 1999, 2009). It is currently listed as Critically Endangered under criterion C2a(ii). This categorisation has been precautionarily maintained since the species was last thought to number fewer than 250 mature individuals and be in continuing decline, with at least 90% of all mature individuals in one sub-population.

This species’s population exceeded 250 mature individuals in 2007 (F. Burns in litt. 2008), and has increased overall since then, with the most recent survey in early 2011 putting the population at 350 mature individuals (E. Duff in litt. 2011). Surveys in recent years suggest that the population of mature individuals has been undergoing relatively minor fluctuations, with totals of 397 in 2010, 322 in 2009 (E. Duff in litt. 2010) and 373 in 2008 (F. Burns in litt. 2008), although such differences may be at least partly explained by annual variation in surveyor experience and other minor variations inherent in replicated surveys. The species has benefitted in recent years from on-going conservation efforts (J. Roberts in litt. 2010), including habitat restoration and control measures against introduced predators.

The results of surveys conducted in 2007 and since indicate that the species may not have met the thresholds for Critically Endangered or Endangered under any of the IUCN criteria for at least five years, and consequently may be eligible for downlisting. It is proposed that the species be downlisted to Vulnerable under criterion D1 on the basis that the population is estimated to number fewer than 1,000 mature individuals, with no evidence of a continuing decline.

It is recognised, however, that the species’s recovery is potentially affected by the on-going threats of changes in land management, the effects of introduced species, disturbance and residential development. The reinstated plans to develop an airport on St Helena and the resulting tourist developments could cause a future decline in the population, in which case the species would be eligible for uplisting. However, while potentially inappropriate tourist developments are a cause for concern, it is not expected that existing plans for the airport itself will seriously impact the population, and mitigation measures have been recommended (N. McCulloch in litt. 2007, 2010).

Comments are invited on the proposal to downlist the species to Vulnerable, and further information would be welcomed.

References:

McCulloch, N. (1992) The status and ecology of the St Helena Wirebird. Thetford, U.K.: British Trust for Ornithology (Research Report 97).

McCulloch, N. (1999) St Helena wirebird: the forgotten plover. Bull. Afr. Bird Club 6: 95-99.

McCulloch, N. (2009) Recent decline of the St Helena Wirebird Charadrius sanctaehelenae. Bird Conserv. Int. 19: 33-48.

This entry was posted in Africa, Archive and tagged . Bookmark the permalink.

One Response to Archived 2011-2012 topics: St Helena Plover (Charadrius sanctaehelenae): downlist to Vulnerable?

  1. Andy Symes says:

    Following government confirmation of plans to construct an airport on St Helena, the RSPB and St Helena National Trust have provided the following response to this proposal:

    Comments on BirdLife International’s proposal to re-classify the St. Helena Plover from Critically Endangered to Vulnerable

    “The St Helena Plover was classified as Critically Endangered (C2a(ii)) in 2007 due to a drop of around 40 % to a low of 208 adults between 2000 and 2005. Since this time annual censuses have consistently been above the 250 threshold ((xˉ (2007 – 2011) = 352.8, SD = 32.7; St Helena National Trust), and although the estimates show considerable variation between years they suggest that the species is no longer declining rapidly. This leads us to consider whether the species should now be re-classified as Vulnerable under option D2.” (BirdLife International, August 2011).

    C2a(ii): Population size estimated to number fewer than 250 mature individuals and a continuing decline, observed, projected, or inferred, in numbers of mature individuals and at least one of the following (a-b): (a) Population structure in the form of one of the following: (ii) at least 90% of mature individuals in one subpopulation.

    D2. Population very small or restricted in the form of either of the following: 2. Population with a very restricted area of occupancy (typically less than 20 km2) or number of locations (typically five or fewer) such that it is prone to the effects of human activities or stochastic events within a very short time period in an uncertain future, and is thus capable of becoming Critically Endangered or even Extinct in a very short time period.

    The RSPB and the St Helena National Trust (SHNT) hereby propose to defer the status re-assessment of the St Helena Plover until the ecological effects of projects associated with the recently confirmed airport construction can be better assessed. Currently there is considerable potential for the population of St Helena Plover to decrease to <250 mature individuals, similar to the size of the population when the species was originally listed as ‘critically endangered’. Particular concerns include uncertainty in relation to (i) the extent and location of developments associated with the airport construction and subsequent increases in tourism, (ii) the extent to which future developments will be required to mitigate any predicted impacts, (iii) the ongoing management and level of use (in terms of number of breeding and productivity) of present and future mitigation sites, and (iv) the magnitude of current and future threats posed by likely increases in alien invasive species.

    There are currently several developments under consideration that could potentially have a very strong influence on key St. Helena Plover breeding areas on St Helena. On 3rd November 2011 the UK and St Helena Governments announced that an airport will be constructed, and there are plans to build associated construction, housing and tourism infrastructure (roads, hotels, golf course). While the location and extent of the airport is relatively well known, no planning certainty exists over associated developments. As we outline in detail below, the associated developments may rapidly change the status of the St. Helena Plover due to various effects. Given this level of uncertainty, we recommend that the species remains at its current status until the final plans for associated tourist developments are known and the cumulative impacts of airport and associated development can be more fully assessed. We consider that a further review of the status of the St. Helena Plover should be deferred until the end of 2012 (or until the effects of airport construction work allow an assessment of potential effects) in order for a better assessment to be made about future implications for the species.

    Whilst the species trajectory and population numbers at present support the re-classification to ‘Vulnerable’, the small size of the island and the limited range of suitable habitat for the species make it exceptionally vulnerable to permanent habitat loss. Permanent habitat loss can be expected from several developments proposed to be situated in St Helena Plover habitat. Too little is known about the flexibility of the species to assess whether habitat compensation measures, created through mitigation work, will deliver the expected results. Because both the extent and precise location of future developments are uncertain, and the responses of the species are unknown, it is currently not possible to produce scientifically valid quantitative population projections for the St Helena Plover. Below we outline in detail the developments that are likely to occur, and the mechanisms by which the St Helena Plover population may be affected. Research currently under way may allow more informative assessments of the likely magnitude of effects. The deferral of the proposed status re-assessment could therefore benefit from highly relevant information being accumulated over the next 1-2 years.

    Land planning on St Helena

    The St Helena Government is currently revising its Land Development Control Plan (LDCP), which is expected to be finalised by 31 March 2012. The LDCP will determine the protection status given to sites that are important for the St. Helena Plover. Depending on what protection status will be assigned to given sites, development on and destruction of these sites would require different environmental mitigation. It is currently not possible to assess whether the protection status assigned to key St Helena Plover habitat sites will be sufficient to require adequate mitigation projects from developers, and thus the extent to which harmful developments may be at least partially compensated for. We therefore believe that a better informed status re-assessment would be feasible after the LCDP has been finalised in 2012.

    Airport construction and mitigation of adverse effects

    The proposed new airport will be built on one of the St. Helena Plover’s breeding grounds in the semi-desert of Prosperous Bay. The construction of housing for workers and transport infrastructure (e.g. a haul road to connect the construction site to port facilities) will also affect suitable breeding habitat. To compensate for the expected losses, a large mitigation project has been in place for the past three years seeking to mitigate the potential negative impacts. This mitigation project aimed to improve habitat in several of the species’ pastureland breeding sites by removing scrub and increasing grazing intensity. This work has been successful in creating suitable breeding habitat in grassland, but the extent to which it will actually compensate for the development is unclear for two important reasons. First, scrub removal and managing appropriate grazing regimes require ongoing funding and effort to maintain breeding habitat, and there is currently no indication that such funding will be available in the future.

    Second, the habitat affected by the airport construction is semi-desert habitat but mitigation focussed on dry grassland habitat. Whether St. Helena Plovers can or will relocate from one habitat to another remains unknown. Furthermore, although a sufficient increase of the population on mitigation areas could potentially compensate for the complete loss of the population in the area affected by the airport, the actually achieved population increase to date has been modest (population in mitigation areas has so far increased by 10 pairs, target increase was 35 pairs). Past experiences with habitat compensation on RSPB reserves have shown that the colonisation of new breeding areas can take up to 10 years. For example, habitat restoration measures by the RSPB for Stone Curlew, Chough, and Bittern all required several years before a positive population response became apparent. We therefore believe that the success (or failure) of the mitigation can only be assessed once construction is underway and the response of displaced birds becomes evident.

    Creation of suitable habitat alone will only lead to higher populations if productivity is sufficiently high. Recent research has shown that nest survival of St Helena Plovers is affected by invasive alien mammals, and it is not yet clear whether predator management will increase productivity. A research project currently under way will provide information on the productivity increase that could be expected from feral cat control. A better assessment of the potential population increase on mitigation areas could be provided at the end of the predator control project (finishing in July 2013).

    Some of the areas chosen to mitigate for negative effects from the airport may in turn be adversely affected by developments associated with the airport. Hence, even if complete mitigation for the airport was accomplished, it is not certain whether the quality of mitigation sites could be maintained given the likely effect of associated developments.

    Given all the above mentioned uncertainties, it is currently not possible to assess whether the population of St Helena Plover will remain at current levels after the airport has been constructed, because the success of mitigation measures cannot be assessed at this time.

    Long-term side-effects of the airport construction

    The construction of the airport was justified by the desire to facilitate financial independence of St Helena through an increase in tourism industry. Annual visitation rates are proposed to increase from currently 900 visitors per year to ~30,000, although it is highly uncertain whether such an increase will occur. Despite lack of evidence for such an increase in visitor numbers, the government on St Helena will plan according to these scenarios and construction of associated infrastructure will therefore occur at the appropriately large scale. These developments have the potential to directly affect St Helena Plover habitat (see below).

    The airport and associated infrastructure will stimulate other business opportunities especially with respect to expected increases in tourism. A popular local recreational activity, off road driving with motorized all-terrain vehicles, will increase with increasing local population and may be promoted as tourist adventure. Most of the off road driving occurs across semi-desert areas populated by the St Helena Plover, in particular Prosperous Bay and Horse Point. The cryptic nests of the St Helena Plover are generally not detected by off-road drivers, leading to inadvertent disturbance or possible destruction. There is currently no enforcement of regulations to limit driving activity to ecologically less sensitive areas, and increases in off-road traffic could lead to significant disturbance and mortality of nests and chicks of the St Helena Plover.

    The import of construction material and engineering equipment that has been used in other parts of the world (e.g. African mainland) as well as the potentially enormous increase in visitors may lead to the inadvertent introduction of non-native species. This pattern has been evident throughout the world on remote oceanic islands. Several invasive alien species already exist on St Helena and are known to negatively affect the St Helena Plover. For example, nest predation by rats and cats leads to lower productivity. Less studied is the influence of invasive plants, several of which are known to degenerate suitable breeding habitat in both grassland areas (e.g. gorse Ulex europaeus) and semi-desert areas (e.g. tungi Opuntia sp., and creeper Carpobrotus edulis). Although there seem to be already sufficient invasive alien species to have detrimental effects on the St Helena Plover, the introduction of additional invasive species that may interact with, or reinforce the effects of already existing alien species, may exacerbate adverse effects. Given the lack of biosecurity procedures on St Helena, and the large volumes of material to be imported for airport construction, it is likely that additional species will be introduced with unknown effects.

    All of the above effects can be expected to gradually increase pressure on the St Helena Plover population that may result in continuing declines of the population.

    Associated developments under consideration

    Besides the airport and its infrastructure, the following associated developments are likely to influence important sites for the St Helena Plover:
    - Hotel and golf course at Broad Bottom, a site that hosts >5% of the global population of the species
    – Temporary housing for airport construction near Prosperous Bay
    – Housing developments for an increasing human population on the island, particularly near Bottom Woods
    – Leisure facilities at Bottom Woods
    – Possible new garbage transfer station at Donkey Plain

    These developments may have both direct and indirect adverse effects on the St Helena Plover.

    If developments involve construction and are planned for important sites for the St Helena Plover, then permanent habitat loss or degradation can be expected. Such an outcome is highly likely for the proposed hotel and golf course at Broad Bottom, and leisure facilities at Bottom Woods. None of these developments have stated whether, or how, they plan to compensate for the loss of breeding habitat, and it is therefore possible that the St Helena Plover population will decrease in response to these developments due to a loss of habitat.

    New housing developments adjacent to important sites for the St Helena Plover may lead to increasing nest predation pressure from domestic animals, particularly cats. Similarly, a proposed new garbage transfer station may attract potential nest predators like rats and cats. A large predator control research project is currently under way to assess the influence of cats on St Helena Plover breeding success. Preliminary results indicate that domestic cats can wander > 1 km from their home and that breeding sites near human settlements are routinely visited by domestic cats. We therefore believe that the construction of human settlements near breeding areas may reduce the quality of the habitat by increasing nest predator density and thus reducing productivity. The current predator control research project will shed light on the likely influence of domestic cats on St Helena Plover nesting success within the next two years, and a deferral of the status re-assessment could benefit from knowledge accumulated during that project.

    Other developments

    In addition to tourism developments, the most important St. Helena Plover site with 20% of the breeding population (Deadwood Plain) has been zoned for a significant wind turbine development. Again, there is no planning certainty and no proposed mitigation in place to reduce the negative effects from wind turbine construction on St. Helena Plover habitat, and it is therefore impossible to evaluate what proportion of that breeding site will be affected. While existing wind turbines had only a small, and mostly temporary effect on St Helena Plovers, loss and disturbance of breeding habitat will be most severe during the construction phase. Due to logistical difficulties in transporting wind turbines, construction of new wind energy facilities is likely to coincide with airport construction to make use of better infrastructure created for the airport. The overall effect of the new wind energy development on St Helena Plover breeding habitat will depend on the location and configuration of the turbines, and cannot be assessed at present. Increases in maintenance traffic may lead to additional disturbance and could potentially increase chick mortality, as St Helena Plover chicks prefer the un-vegetated service roads where they are vulnerable to traffic.

    In summary, we feel that a better informed status re-assessment could be performed after the major developments planned for St Helena have been confirmed, and the extent and magnitude of their impacts on the St. Helena Plover can be estimated with greater precision than is currently possible. Developments over the next 2 years may indicate that the St Helena Plover is sufficiently flexible to withstand developments that perform environmentally responsible mitigation. Alternatively, developments may reduce the present population to less than 250 mature individuals and induce an ongoing decline of the species through increasing pressure on the remaining habitat – thus re-instating the precarious state of the St Helena Plover population that originally led to its ‘critically endangered’ status.

    RSPB:
    Tony Prater
    Fiona Burns
    Steffen Oppel
    Juliet Vickery
    James Millett
    Jonathan Hall
    Sarah Sanders
    Tim Stowe
    Dieter Hoffmann

    St Helena National Trust:
    Rebecca Cairns-Wicks
    Jamie Roberts
    Chris Hillman
    Eddie Duff
    Kevin George

    External:
    Neil McCulloch

Comments are closed.