As a species, humans are far-and-away the most capable organisms with reference to the ability to modify the environment. After us, the impact of other organisms falls off pretty fast.
Critters, such as locusts, come to mind. Numbering in the billions, these voracious insects can bring widespread devastation to seasonal plant growth in Africa. Bison, which once numbered in the tens of millions on this continent, could eat their way through untold tons of grass on the Great Plains. Both of these examples, however, are of a short-term nature.
When we speak of years-long transformations we have to look at other things like coral. It is said the Great Barrier Reef, stretching well over 1,000 miles along the Australian coast, is the single largest structure created by living organisms. That's impressive. But it takes unfathomable numbers of coral polyps to make this happen.
Taken as individuals, though, none of the above-mentioned species measure up. I can only think of one lowly shy animal even in the ballpark with humans in terms of long-term environmental shuffling. As it happens, this critter was also critical to the exploration and settlement of a large part of the U. S. and Canada. I'm talking about the beaver (Castor canadensis).
Once numbering as many as 90 million individuals, this animal was a primary motivator spurring early forays into the North American west. Or at least its hide was. Thousands of pioneering fur-trappers and voyageurs ventured into parts unknown seeking the lush waterproof fur of this large rodent to meet the demands of clothing makers, both here and in Europe. Fortunes were made in the fur trade (think John Jacob Astor or Hudson's Bay Company). Though once silk became the hot fabric du jour, demand for beaver fell and the animal began a slow recovery from near extinction.
Beavers, which can reach up to 60 pounds, are the second largest rodents in the world and continue to grow until they die. Armed with four impressive incisors, these animals are well known for their ability to fell rather large trees. It's an herbivore feeding on shoots, leaves and young wood.
In smaller watersheds their reputation as dam builders is storied. Entire drainages can be changed for decades by generations of beaver families erecting successive dams. This often creates multiple layers of terraced still pools which alter the plant life for miles. In this way, the animal is credited with preventing some erosion and being nature's "kidneys," by purifying water. In forested areas this goes mostly unnoticed. But when the animals ply their trade in urban zones, problems arise. Damage to landscapes can be severe as beavers saw down trees along rivers, mostly at night. Often trappers are brought in to eliminate nuisance animals.
Beavers are said to mate for life and build impressive domed homes known as lodges. When rivers are too large to dam, the animals simply bore into the banks and create makeshift dens there. Inside, families consist of adults, yearlings, and kits (young). When beavers are two years old, they leave the lodge to find new territory.
This is an animal well-suited to its watery environment with webbed hind feet for propulsion through the water while its large, fleshy, scaled tail is used as a rudder. Extremely thick gray fur acts as insulation from the cold underneath a blanket of rich brown-to-black hairs.
Even in the absence of dams, it's not hard to find evidence of beavers. Woodchip piles around gnawed trees, matted runs leading to water, and curious piles of fresh twigs (collected in fall for winter food caches) stacked in the water are just a few obvious signs.
Seeing them is slightly tougher. Being nocturnal animals, your best bet is during dusk or dawn when beavers are more active. They are fairly wary critters and usually shun close approach. When alarmed, beavers perform a signature alarm by loudly slapping the water with its flat fleshy tail and submerging. It sounds like someone doing a cannonball dive.
While not nearly as numerous as it once was, the beaver remains historically significant. It's Canada's national animal and is featured on the reverse side of their nickel. It was also the mascot of the 1976 Summer Olympics in Montreal. This meek retiring critter is still sought by fur trappers even now. The glory days of the trade, however, ended more than a century and a half ago.