Research Briefs

Short accounts of papers from EDG researchers.

Counting species is an inaccurate science

Knowledge of the number and distribution of species is fundamental to biodiversity conservation efforts, but this information is lacking for the majority of species on Earth. Consequently, subsets of taxa are often used as proxies for biodiversity; but this assumes that different taxa display congruent distribution patterns. For example, one method is by counting a well-known group, such as birds, and assuming they represent the diversity of other groups.

A group of researchers at ANU, led by Martin Westgate, has compared many of these different estimation methods to test their validity. They whittled down over 8,000 biodiversity papers to 81 papers that could be directly compared. Their comparisons found a serious lack of consistency between the different assessments of biodiversity. In particular, they found that studies at different latitudes or spatial scales rarely find similar results, even when they consider the same groups of plants or animals.

These results undermine the assumption that a subset of taxa can be representative of biodiversity. Therefore, researchers whose goal is to prioritize locations or actions for conservation should use data from a range of taxa.

Reference

Westgate MJ, PS Barton, PW Lane & DB Lindenmayer (2014). Global meta-analysis reveals low consistency of biodiversity congruence relationships. Nature Communications 5:3899. DOI: 10.1038/ncomms4899

Inferring extinctions from sighting records

The decision of declaring a species has gone extinct is critically important to conservation management (see Decision Point #38). A range of mathematical models has been developed to infer whether a species is extinct based on a sighting record. Although observations have variable reliability, current methods for detecting extinction do not take this variability into account.

To rectify this, Tamsin Lee and colleagues have developed an approach, based on a Bayesian method, that consider certain and uncertain sightings throughout the sighting period. They then applied their method to estimate the probability of whether the Caribbean seal, black-footed ferret, greater stick-nest rat and lesser stick-nest rat are extinct. As further examples, Birdlife International provided the sighting records for the Alaotra grebe, Jamaica petrel and Pohnpei mountain starling with prior probabilities for extinction. Their results were compared with existing methods, which ignore uncertain sightings. They found that including uncertain sightings can considerably change the probability that the species is extant, in either direction. However, in these examples, including the quality of the uncertain sighting made little difference. However, when uncertain sightings are ignored, their results agree with existing methods.

Estimating the probability that a species is extinct based on sighting records is important when determining conservation priorities and allocating available resources to management. Having a model that allows for certain and uncertain observations throughout the sighting period better accommodates the realities of sighting quality, providing a more reliable basis for decision-making.

Reference

Lee TE, MA McCarthy, BA Wintle, M Bode, DL Roberts & MA Burgman (2014). Inferring extinctions from sighting records of variable reliability. Journal of Applied Ecology 51: 251-258.