I worked in air quality, water quality, range, wildlife and forestry with the U.S. EPA, and the U.S Forest Service. I did that in Nevada and eastern Oregon for over 30 years. Over that period, it was natural to develop an abiding love for the island forests and woodlands of the interior. and a deep interest in their development since the last glaciation. There can be few places more welcoming on a blistering summer day than under the sun-filtered canopy of an old-growth Ponderosa pine forest, and nothing more sublimely elegant.

How did they get here and how are they doing? They’ve been around a long time, and there should be more big ones than there are. That’s too bad since the plate-like bark, half a foot thick and often outlined in a mosaic pattern of fire-hardened scars – is nearly impervious to any but the largest blazes. Properly managed, these old-growth forests are the best hedge we have against wildfire in this widespread ecosystem. Even in death, the searing heat they’ve experienced over their 300-500 year life-span can seal the trunks off from rot for the next 80-100 years. They are then resurrected as crucial habitat for all the cavity nesting animals. Those creatures can, in turn, play an important role in kick-starting the next forest stand.

I’ve come to feel that, with climate modification a growing planetary concern, the interior western forests offer a crucial reservoir of genetic diversity. If there’s any hope of coping with the changes which might result from a catastrophic shift in the climate regime, it resides in the gene pool of communities like these dryland forests.

Ponderosa Pine (Pinus Ponderosa) defines the margin of many interior forests in the western United States. It’s the most drought tolerant giant conifer in North America. Paleobotanists examining the fossil record have found evidence that, in the recent past, forests of Ponderosa have existed in many different configurations. Plant associations which have no current analogs can be found in that record, an indication that “Range shifts occurred that could not have been predicted ...” and that these shifts “…apparently led to anomalous species associations“

The implications of this research are of major importance. They offer up some hope of coping with the changes in the variation of seasonal precipitation and temperature which will result from broad-scale climate modifications.

That’s because, from the fossil evidence mentioned above, we now know that the genes of these forest types represent a large reservoir of unexpressed diversity. This diversity provides a crucial hedge against climate change. It allows drought tolerant Ponderosa pine forests to adapt quickly to altered conditions. That’s happened many times in the past, that’s what this evidence tells us.

Unfortunately, this diversity has gone unacknowledged resulting in the failure of silvicultural theory on both public and private lands in the West. Foresters chose to “liquidate” stands of old-growth Ponderosa Pine in favor of what they promised would be faster growing stands of other conifers. The idea was to make more money off these new forests. But this attempt at forcing moderate to low-elevation sites to produce as if they were industrial forest plantations has failed. Insects, well-adapted to that same variation in climatic forcing, re-worked overstocked stands of drought-intolerant species, just as if there had been a change in the climate.

The message is clear: at the forest margin, trees other than Ponderosa pine are a minor component, so Ponderosa is what should be there. But since they are slow-growing many of these stands cannot be economically cropped now or in the future. Selective cutting, with its much lower rate-of-return, should be the only way we remove trees from these forests. The fact is, these pine forests are much more valuable for their water, forage, recreation and soil stabilization potential than as poorly managed quasi-industrial croplands.

We need to to insure the health of these forests. In their genes they carry a message from a long-distant past, one that may help us find our way in a very uncertain future.

1.  Spaulding, W. G. The last glacial-interglacial climatic cycle: its effects on woodlands and forests in the American West. in Eight North American Forest Biology Workshop (Dept. of Forest Resources, Utah State Univ., 1984).