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March 16, 2023

The preservationist group NatureServe just released a report concluding that some 40% of animal species in the US will go extinct in the near future as a result of climate change. 

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Their predictions may turn out not to be quite accurate, since there are other factors at work that determine which species survive and which go the way of the dodo bird and ivory-billed woodpecker. The analysis the report depends on has been severely criticized for lack of rigor by Canadian and Finnish biostatisticians. Anticipated losses among a small percentage of already dangerously endangered species is applied to the vast majority of U.S. animal populations showing no signs of diminishing in numbers. The polar bear, to the contrary, has recovered dramatically from a low of less than 10,000 adults in 1975 to more than 30,000 in the most recent surveys.   

Nature is a harsh taskmaster. Climate is always changing, but at a differing pace at various times and places across the globe. Rapid changes will put severe stress on species lacking adequate genetic resilience and a deep enough gene pool.

Changes in physical conditions (weather extremes and habitat alteration) force species to adapt to new conditions or go extinct. Geographic isolation often leads to new species evolving from and replacing a parent group. Few old-time species and genera can trace their existence back in time a million years.

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The report found “habitat degradation and land conversion, invasive species, the damming and polluting of rivers and climate change” as the primary factors forcing susceptible species toward the brink of extinction.   

Yet it is impossible not to sense ambivalence after reading through the conclusions. There are species under duress that would find themselves threatened whether or not man had ever settled in North America.    

The multiple comings and abrupt departures of the great continental glaciers (at times covering more than a quarter of Earth’s land surface) resulted in extinction for many species that were unable to cope with dramatic swings in temperature and loss of vegetation and prey that were far more extreme than those anticipated in the report.   

The combined threatened and endangered species currently listed by the U.S. Interior Department’s Fish and Wildlife Service and the National Marine Fisheries Services of the U.S. Commerce Department number 731 animal species and 941 plant species. The number of known vertebrate species in North America totals nearly 3,000. The number of plant species, nearly 19,000.   

There continue to be newly discovered species in little explored habitats, previously unknown to science. The total number of species globally is at best a working estimate on the part of taxonomic experts.  

Simple division suggests that substantially fewer than 40% of the total number of animal species are currently threatened or endangered. Invertebrate species (primarily insects and other arthropods), excluded from the study, far outnumber all vertebrate species. The estimated numbers of beetle species in North America alone, some 30,000, dwarf the vertebrates ten to one!