Institute For The Future

Exinction Risks Underestimated -- NATURE

A new article in Nature argues that current models for estimating extinction risks underestimate the impact of forces beyond birth-death ratio and environment. As a result, biologists may be missing potentially significant extinction threats.

From the Nature summary:

Extinction risk in natural populations depends on stochastic factors that affect individuals, and is estimated by incorporating such factors into stochastic models. Stochasticity can be divided into four categories, which include the probabilistic nature of birth and death at the level of individuals (demographic stochasticity), variation in population-level birth and death rates among times or locations (environmental stochasticity), the sex of individuals and variation in vital rates among individuals within a population (demographic heterogeneity). 

The BBC explains:

As well as the male-to-female ratio, they point to the physical size of individuals in a species, and some aspects of behaviour.

They found that when populations are small and vulnerable, changes in the sex ratio can have a huge impact on survivability.

Overall, their new model of risk suggests that some species are at much greater likelihood of extinction than normally assumed.

Professor Alan Hastings from the University of California, Davis, told the BBC: "With some species, if the numbers are going up and we can protect them then we're probably doing OK.

"But there may be many species - and some will not be the large, charismatic ones, but things like insects and other smaller ones that are still very important - where we may be underestimating the risk by quite a bit."

The International Union for the Conservation of Nature (IUCN) currently lists over 16,000 species as threatened by extinction, including 70% of plants, 33% of amphibians, 25% of mammals, and 12% of birds.