Dave Hallock, Eldora.  A recent assessment of global wildlife numbers concluded that they had declined by over half since 1970. In other words, the world has just half as many animals as it did forty years ago. That's a statement that stopped me in my tracks. The World Wildlife Fund looked at the trends in over 10,000 populations of 3,038 vertebrate species (mammals, birds, reptiles, amphibians, and fish) and concluded that there had been a 52% decline between 1970 and 2010.

The declines varied with geographic area and type of animal. The most dramatic decreases occurred in South America, followed by the Asia-Pacific region. The declines were highest in freshwater vertebrates at 76%, while terrestrial and marine animals saw declines of almost 40%.

The primary causes were habitat loss or degradation (the conversion to agricultural land, urban development, and energy production) and exploitation (fishing and hunting). Pollution, disease, invasive species, and climate change were other causes of animal declines.

North America fared better, with only a 20% decline. Amphibians, fish, and reptiles declined. However, mammals and birds increased in number. In the American West, most ungulates, such as elk and deer, are managed to maintain their populations, while many large carnivores, such as wolves and grizzly bears, are numerically expanding.

Bald eagles and peregrine falcons are recovering. But before we pat ourselves on the back, remember that this study looked at changes from 1970. The time of greatest animal decline in the American West was the 1800s and early 1900s. Since then, law enforcement and reintroduction programs, combined with suitable habitat on National Forests and Parks as well as large private ranches and open space, has allowed for a bit of recovery.

The population status and trends of vertebrates in Boulder County mirror the trends of the American West. Bison, pronghorn, gray wolf, grizzly bear, swift fox, and black-footed ferret were extirpated from the county by the early 1900s. Elk were virtually wiped out of the county by the early 1900s; they were reintroduced and have thrived in the mountains, but are generally absent from most of the eastern county. Bighorn sheep were also extirpated from the county by the early 1900s; they were reintroduced into the North St. Vrain canyon, where a small population still persists. Canada lynx were also removed from the county, but will likely return with their reintroduction into Colorado.

The mountainous portion of the county has seen the recovery of many animal species during the 20th century, as there is less human development and habitat fragmentation, while the vegetation is dominated by native ecosystems. It is possible that someday we may even see wolves return to the western county as they expand their range throughout the American West.

But the eastern county, the plains, are a different story. The high degree of urbanization and agricultural development has left only a small patches of native ecosystems and a landscape that is highly fragmented. Large ranging mammals such as bison and pronghorn could not persist as free-ranging animals. Elk, while thriving in the mountains, only come down to the plains on occasion, and primarily just the western fringe.

A host of other plains species have been undergoing a long-term decline, including lark bunting, northern harrier, horned lark, burrowing owl, loggerhead shrike, grasshopper sparrow, and white-tailed jackrabbit.

County-wide declines are also occurring for most amphibians. The reasons appear to be a combination of disease, invasive species, and habitat loss.

So, while some animal species have recovered into available habitat during the 20th century, others continue to decline in the county.

Following are some of the November nature happenings in the Nederland area:

Elk will wind down their mating activities. The timing of their movement to lower elevation varies with each herd. Some have already made the trek, while others will let the increasing snow depth push them down.

Black bears continue to find winter dens for hibernation, with the second and third weeks of November being the peak time for males. Moose will also wind down their breeding activities. Mule deer breed in November and December. Most have moved down to the foothills.

The last ground squirrels and chipmunks will go into hibernation, though they still may pop out from time to time during mild weather. Mice and pack rats continue their migration into our cabins.