North american dating sites
Our present time is marked by rapid and profound change. How can we know the degree to which our activities are changing the long-term health, composition and extent of North American forests if we don’t understand what they once were and how they became what they are today? What we need is, well, something more like a Hollywood movie.In this first of a two-part series, we’ll see that the natural baseline is a moving target. The more familiar, seed-bearing conifers came on the scene around 300 million years ago, and the flowering or broadleaf trees arrived 140 million years ago.These episodes of glaciation are thought to be caused by cyclical changes in the Earth’s orbit, tilt and orientation, collectively known as Milankovich cycles.At the peak of glacial periods, ice can cover 75 percent of North America, nearly two miles thick in places and weighing so much that it can depress the continent by as much as 1,000 feet.
At Elite we simplify socializing and make it easy to get to know people you click with totally free!When it had grown to maximum size, some seven million square miles, it broke the back of the continent. No, this is not a preview for another post-apocalyptic Hollywood survival movie.This catastrophe is a major part of Earth’s recent history and is best known for cavemen, mammoths and, well, ice. It is less well-known as the engine of change in North American forests for the last two and a half million years: Forests were consumed, driven south, rearranged and reordered.Diverse, ancient forests of the Pacific Northwest have been clear-cut and replaced with a monoculture of skinny, young trees in a checkerboard pattern right up to national park boundaries.Each of these views is but a snapshot in time, and none is sufficient for a proper understanding of our forests.