Evaluation of the impact of extreme floods on the biodiversity of terrestrial animals

Highlights: • The factors influencing the degree of impact of floods on biodiversity were boiled down to four. • We proposed TBI and ABI indicating the overall and average impacts of floods on biodiversity, respectively. • The calculation method of TBI and ABI considered both the number of species and four factors. • The impact of floods on biodiversity is different in different submerged areas and flood occurrence time. Extreme floods seriously affect the biodiversity of terrestrial animals (birds, mammals, reptiles, amphibians, and insects). The degree of impact depends on many factors, e.g., animal characteristics, natural conditions, and flood characteristics. Previous evaluation methods are not suitable for assessing the impact of floods on the biodiversity of all species in the entire submerged area, nor do they accurately reflect variability in the degree of impact. First, the influencing factors were boiled down to four: ratio of flood duration to survival time of animals in floods (D), ratio of flood depth to plant height (S), migration ability of animals (M), and temperature (T), which are represented by a coefficient I. Then, we proposed a calculation method for I based on the four factors. Third, we proposed the total and average biodiversity impact indices, namely, the TBI and ABI, respectively, indicating the overall and average impacts of floods on biodiversity in the submerged area, with the calculation method considering both the number of species and I. An extreme flood was simulated to obtain the flood parameters. In addition, we analyzed monthly changes in partial influencing factors. Finally, the impact of extreme floods on the biodiversity of terrestrial animals in the submerged area was evaluated monthly, and it was found that (1) TBI and ABI changed with space; (2) the ABI of different animals in descending order were mammals, insects, reptiles, amphibians, and birds; (3) the ABI of different land use types in descending order were cropland, orchard and shrubland, grassland, and forest and for TBI were orchard and shrubland, cropland, forest, and grassland; and (4) the TBI and ABI of different animals and land use types changed over time. The proposed method and indices are suitable for assessing the impact of floods on the biodiversity of any organism in any area.