Winter fauna assessments for environmental impact assessments

The EPBC Act and EPA websites frequently publish fauna survey and assessment reports. In addition there are numerous other fauna surveys undertaken to support mining applications or native vegetation clearing permit applications to the Department on Mines and Petroleum (DMP), Department of Environment (DoE), Department of Parks and Wildlife (DPaW) and the Environmental Protection Authority (EPA) that are never made public. Some of these vertebrate fauna surveys are being undertaken in winter. Here we question the wisdom of winter fauna surveys for supporting EIAs, particularly in the Goldfields and the Pilbara.

The EPA/DEC Technical Guide – Terrestrial Vertebrate Fauna Surveys for Environmental Impact Assessment recommends the timing for vertebrate fauna assemblage surveys based on whether the survey is targeting reptiles, amphibians, birds or mammals.

It is appreciated that reptile activity and thus trapability varies with the seasons, but by how much has been rarely documented for Australia. A multiple site survey using a standard trapping protocol at Ora Banda in the Goldfields recorded significant variations in the number of reptile species and the number of individuals caught among seasons (Table 1; Thompson 2005). For mammals, the number of species recorded showed much less variation, but the number of individuals varied significantly. The mammal species count was influenced by single captures for four species in April, December and January.

Table 1. Variability in reptile and mammal species and numbers over 11 sampling periods

Thirteen mammal species and 56 reptile species had been trapped in the Ora Banda survey area. It is therefore evident that no one survey period recorded all species, but surveys undertaken in April and June caught insufficient animals to provide a reasonable indication of the small vertebrate fauna assemblage in the area.

We surveyed in the Hamersley Ranges in March and November 2008 to assess temporal and spatial variability of terrestrial vertebrates using 54 sites with an identical trapping protocol (Thompson et al. 2010). Daily minimum and maximum temperatures at Tom Price, the nearest weather station to our survey sites, were significantly higher during our March survey (19.8^oC and 37.4^oC respectively) than during our November survey (16.4^oC and 33.9^oC respectively). It rained on two of the 14 survey days during March (12.4 and 0.4mm respectively) and there was no rain during the November survey. Higher maximum daily temperatures in March compared with November seemed to be the main reason for a significantly higher number of individuals being caught (Table 2). We concluded from these data that surveys undertaken in the Pilbara during the cooler months would only record a small proportion of the trappable reptile species in the area and normally only the common species.

Table 2. Total number of individuals and species by family for the March and November surveys

These data would indicate that winter fauna surveys in the Goldfields and the Pilbara are inadequate to adequately represent the trappable vertebrate fauna in these areas. These data would also suggest the survey timing in the EPA/DoE/DPaW guidance statements are too wide and need to be narrowed and more focussed on the warmer summer months, particularly if the full suite of reptile species are to be recorded.

The EPA’s (2002) Position Statement No 3 Terrestrial Biological Surveys as an Element of Biodiversity Position Statement No. 3 indicates that the EPA requires sufficient information to address both biodiversity conservation and ecological functional values within the context of the type of proposal being considered and the relevant EPA objectives for the protection of the environment. This statement goes on to say that best practice assessments require that biodiversity be considered to have two key aspects; namely:

1. Its biodiversity value at a genetic, species, and ecosystem levels; and
2. Its ecological functional value at the ecosystem level.

It is not possible without a reasonably complete species list and a good understanding of the structure of the fauna assemblage in a project area to assess potential impacts at an ecosystem level or on the functional value of the ecosystem. Winter surveys are unlikely to provide the necessary fauna data to meet the EPA’s stated requirements that would enable a consultant to assess impacts on the functional vertebrate ecosystem.

Environmental consultants will continue to undertake vertebrate fauna surveys in inappropriate seasons while regulators continue to accept fauna surveys undertaken during this period as providing adequate information upon which to assess potential impacts on the vertebrate fauna.