I’ve been thinking a lot on this trip about differences between the arid West and the moist temperate Northeast. There’s a lot, it turns out, and they primarily reduce to climate, landform/topography, and land use history.
For example, the Rio Grande valley around Santa Fe is very dry – ~14 inches of rain a year. And if you follow the valley 50 miles southwest and down-elevation to Albuquerque, it’s even drier, with juniper/pinon woodland giving way to grassland scrub on the edge of the Sonoran desert. But all you need to do is go up in elevation to rapidly move through different landscape types. Dry scrub moves to dry woodland moves to moister Ponderosa forest, to yet wetter spruce-fir forest, to very snowy subalpine forests, to alpine tundra, as you climb, like in this image from the Colorado Rockies.
And aspect makes a major difference as well, with different aspects being hotter or cooler and wetter or dryer with sun access and weather patterns. And riparian corridors add major structural and species diversity everywhere they occur, both in the forested mountains and the dry basins. So what this adds up to, from an ecosystem perspective, is that landscape-scale structural diversity is very high in much of the arid mountain West. The number of structurally distinct plant communities accessible in two day’s walk, or an hour’s drive, from many places is staggering. However, within many of those plant communities, species richness is very low both in general and compared to historical levels. This is both because of the arid climate (i.e. water as a major limiting factor), and because of a century and more of overgrazing, fire suppression, climate change, and widespread removal of native people and traditional land management practices.
In the moist temperate Northeast, annual rainfall is high enough that even third-or-fourth-growth forests, regrowing from overgrazed pasture land, contain quite a high level of species richness compared to arid Western forests*. But, also unlike most of the West, landscape-scale structural diversity is very low throughout most of the Northeast. It’s the land of urban and suburban landscapes, annual crops and pasture, 80-year-old full-canopy even-height forest, and very little else.
One reason for this is, again, climate and landform. 40-50+ inches of rain a year, plus heavy winter snows, means there’s more than enough water for closed-canopy forest to grow in all but the driest or thinnest soils. And the Northeastern hills and mountains are old, low, eroded, and gentle enough that only the steepest cliffs, thinnest-soil rock faces, and very highest elevations have enough belowground competition or natural disturbance to limit tree growth. But it’s also because of our particular land use history defined by: very early widespread removal of native people; multiple, protracted deforestation events; extirpation or extinction of apex predators and keystone herbivores; and pasture and farm abandonment throughout the region in the early 20th century leading to monotypical regrowth. See Wessels and Cronon for more on this land history.
Early-succession environments, patches of meadows and shrublands in the forest, and open savannas and woodlands with larger trees are all very rare in the Northeast. And that means that the species diversity associated with those landscape types is very rare. And that means that it’s very hard to live off the land in the Northeast, because those mostly missing landscape types – like the oak savanna below – are the ones that have the most available niches for wild foods, medicines, fiber plants, and game animals!
More to come on regions other than the Northeast and the arid mountain West, and also on directions for land stewardship in these different regions based on this line of assessment.
*Although, herbaceous spring ephemerals and valuable slow-growing ethnobotanicals, (which are often one and the same) are underrepresented in current-day northeastern forests. And, of course, many of the keystone animals.