Scientists in general and particularly geologists measure time on our planet in epochs. For example the time from two and a half million years ago until twelve thousand years ago is called the Pleistocene. This time period was characterized by a series of long glacial periods. The current epoch is called the Holocene which began with the worldwide recession of the glaciers.
Recently some scientists have called for the naming of a new epoch called the Anthropocene, characterized by human influence on the planet due to our transformation of the atmosphere over the last two hundred years. Others contend that the start of the Anthropocene should be counted as starting much earlier. Modern humans have influenced the planet by churning the biosphere for close to a hundred thousand years. Our mobility has resulted in the movement, occasionally purposely, of many many plants and animals.
Wheat originated in Near East, corn in Central America, and rice in Far East. All are purposely cultivated world wide. The inadvertent introduction of some species has been the ruination of others. The inadvertent human dispersion of the black rat is a good example. It has caused the extinction of many bird, reptile, and other small vertebrate species across the planet.
The honey bee originated in Africa, and migrated to Europe. It was brought to North America by the colonists for honey production and has been a resounding success. Annually fourteen billion dollars worth of crops are dependent on honeybee pollination in the United States alone. Ironically the honeybee brought to North America by humans is now threatened by humans by the use of a class of insecticides known as neonicotionoids.
Non native earthworms were also brought to North America by the colonists but this time the importation was accidental. They came as part of the ballast of ships and in the soil of potted plants. Their introduction has been a mixed bag. Whereas home gardeners and those who fish extol the virtue of the earthworm, they are actually harmful to forests of northern North America.
Glaciers advanced to about the Missouri and Ohio Rivers and wiped out earthworms, if there were any to begin with. After the glacial recession, the forests returned and adapted in the absence of earthworms. The normal condition of the forest floor is a thick layer of slowly decomposing leaves. The presence of earthworms accelerates this decay, removing an important organic layer that serves as seed beds for saplings, ferns, and wildflowers.
One of the newest accidental imports is another ant, called the Crazy Ant for its erratic behavior and tendency to swarm. It first showed up in Houston TX and has been seen in southeast TX, southern Louisiana, southern Mississippi and and much of Florida. Where it occurs it either kills or drives out most other species of insects, spiders, small reptiles and birds. They will nest just about anywhere but are particularly fond of electrical wiring, causing a 150 million dollars a year damage in Texas alone.
We certainly live in a time of dramatic global human influence. We continue to change the composition of the atmosphere and hence the climate. We are making the oceans more acidic. We are dispersing uncountable numbers of species, generally with negative impact. And all these effects are causing extinctions of flora and fauna. My question for you is should we?