Are we about to lose 40% of our species?
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.
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.
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!
Unless the total number of species becomes a better-known quantity, percentages applied to imminent extinctions remain in the realm of speculation.
On the sandy, low plains of south Florida there are scattered remnants left behind by now long-extinct vertebrates such as the wooly mammoth and saber-toothed tiger (Smilodon) with others forced to flee the massive ice sheets. Herbivores migrated south to find forage. The predators followed. The rangeland beset with drought and dusty conditions became inhospitable to large mammals that had previously grazed (or hunted) the prairies to the north. Many large mammal species became extinct, never to return to their original ranges following the retreat of the ice.
As recently as ten years ago, south Florida experienced a month-long cold spell that chilled inshore waters sufficiently to kill off many cold-sensitive tropical fish, including the snook, a species that inhabits tropical waters from Florida south to Brazil. Thousands of dead fish rotted in the coves of the Indian River Lagoon from Fort Pierce northward to Jacksonville. Afterward, snook were again limited to their former range.
Decades of warming winters had enticed dispersing snook northward into waters beyond their normal range. When the cold weather arrived suddenly, they were unprepared to deal with it. A snook's metabolism shuts down abruptly below 60-degrees Fahrenheit.
Natural fluctuations within climate extremes place vulnerable species under threat of extinction, or more likely extirpation from their former range. The result may be unavoidable, no matter how much federal money is allocated to save Humpty Dumpty.
Exotic big snakes have taken over the Everglades, uninvited and unwelcome, in recent decades. The constrictors do not find even an occasional frigid outbreak to their liking. Natural variability can be a good thing, too!
Yet taking prudent measures to preserve habitat and closely regulating bag-limits for hunting and fishing will help preserve species with sufficient genetic diversity to survive stresses sure to come. Direct intervention may help some species but, in the end, it will not necessarily preserve many species already teetering on the brink. The ivory-billed woodpecker may have sung its swan song.
Before being stampeded into an enviro-frenzy by advocates who like to remind us of once common species no longer around to cheer and comfort us, it should be realized that some of those alleged 40% are struggling to maintain their sparse numbers and have been so for some time before climate change became a pressing issue. Only the most genetically fit will survive the vicissitudes of organic change (classical evolution) that necessarily winnows and sifts through all contemporary life forms over time.
The most familiar birds seen and heard in our urban neighborhoods, and fields and woodlands are very likely to be enjoyed by future generations of bird-lovers and casual observers. The robins, cardinals, sparrows, blue jays, doves, and blackbirds are excellent candidates to survive despite a continued modest rate of warming that may persist for the remainder of this century (or not).
There are also the less frequently seen or heard species like wood thrushes, warblers, and the enigmatic whippoorwill that may not enjoy as secure a future. Whippoorwills and their close cousins, the chuck-will-widows are not being heard as frequently as a decade ago. Habitat loss from encroaching suburbanization may account for their decline in numbers.
Yet it is a sobering fact biologists estimate well more than 99% of all species having ever lived on the planet have since gone extinct. New species, genera and higher taxonomic classifications have then arisen in timed sequences to take their places.
Paleontologists count at least six great die-offs during the nominal 3.5 billion years of life on the planet. Whether the current Holocene Period will usher in the latest great extinction remains to be seen. I am inclined to believe we may be hearing more crying "wolf," absent a catastrophe comparable to the sudden arrival of the big asteroid sixty-five million years ago.
William D. Balgord, heads Environmental & Resources Technology, Inc. in Middleton, WI, and is a Contributing Writer for the Cornwall Alliance for the Stewardship of Creation.