How to evaluate and rescue endangered species?

Extinction of species is a natural process, yet human prosperity has eroded the habitats of millions of species, as a result, many species have disappeared (e.g., white-flag dolphin, Chinese paddlefish) or is going into extinction (e.g., Chinese sturgeon), but without coming of new species. Although the IUCN has established the quantitative standard of endangered species, it is more symbolic rather than practical, as it is impossible for all species to predict their future fates only through the same population dynamic model. On the endangered causes of species, there have many theoretical concepts based on the dynamics of population density (such as minimum viable population, effective population size, population bottleneck, founder effect, Allee effect, extinction vortex), which generally have poor operability, and thus is of little significance to the practical guidance of conservation biology. In this paper, a conceptual model of regime shift of species status is proposed. Species status depends on its composite survival fitness f(s) and extinction risk (R) to external environments, which are affected by integrities of living space and ecological processes, food availability, and resistance to fatal artificial or nature disasters. f(s) is determined by the product of the fitness of several determinant survival factors (s1, s2, s3......): f(s) = f(s1) f(s2) f(s3)......, and f(s) takes values of 0-1, with 1 being the maximum fitness (ideal status) but with 0 being complete absence of fitness. Therefore, zeroing of any determinant survival factor f(s) would indicate species extinction (buckets effect). Index of species status [H(f, R)] is determined by f(s) and R. f(s) can be used to assess and predict the extinction risk of species (e.g., it can be divided into 3-4 risk levels), the dynamics or processes before the critical point can be used as an early warning signal of speceis extinction, and the tipping point of species rescuing can be regarded as the lowest target of protective intervention. Of course, here is just a conceptual model, and each f(s) still needs to be detemined and tested by data from real species. © 2020 by Journal of Lake Sciences.