Category Archives: plant communities

Blind to the End Game

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It was quite a few years ago now, but an editorial in the Portland Oregonian came across as a tout-sheet for the conversion of cut-over timberlands to real estate holdings (Absence makes the heart grow fonder, Jan 2nd, 2010). It only served to drive home the words of philosopher George Santayana:

Those who cannot remember the past are condemned to repeat it.

The entire premise was underlain by a set of faulty assumptions that contradict much of what the article was trying to sell.

Let’s start with some ecological reality that rarely sees the light of day. Eastern Oregon
has suffered dramatically from the absurd notion that industrial forestry of the type practiced in Western Oregon was ever marginally viable in the dry forests of the interior. These two ecologically distinct parts of the state were for decades treated as one and the same for the purposes of projecting timber harvest, when nothing could have been further from the truth.

That’s something even new Oregonians understand intuitively. You can see it with your eyes if you bother to look. The editorial board, as one egregious example, makes no mention of the stark differences in climate and precipitation that drive forest growth. It’s a fact that industrial forestry may not even work on the West side. Chris Maser, Jim Trappe and their co-workers hypothesized long ago that continuously cropped forestlands are prone to failure because they eliminate the carryover components – the elements necessary for the re-generation of forest stands.

We certainly have enough evidence to state conclusively that it doesn’t work at all in the dry montane forests of the interior West. That’s an important story that The Oregonian has never even bothered to cover, yet that narrative challenge needs to be taken up by everyone in the state who claims care about the future of its forests.

What it means is this: none of the management plans for cutting hundreds of millions of board feet per year in Eastern Oregon were remotely sustainable. Public and private foresters, who logged the fire-resistant old-growth Ponderosa pines and replaced them with what they thought would be fast growing fir, were badly fooled. The resulting stands of sapling-choked forest have been magnets for insects, disease and fire.

Increased susceptibility to these agents has been couched in the gobbledygook of forest health. The reality is much simpler. These “problems” are a manifestation of the natural
thinning processes inherent in heavily over-stocked and, in this case, poorly managed stands. It’s what these forests undergo in re-establishing themselves. The mature trees that are the result of this thinning action from these agents, and that are the best adapted to resist them once they’ve fully developed, were cut down and hauled away. Sustainable timber harvesting would have identified these relationships as part of the information gathering process. Either willfully, or because of blind ignorance, that didn’t happen. That isn’t much of a business model, certainly not one with any staying power.

The yield increases never occurred and everyone now admits that Ponderosa is best suited to drier sites. The cost of managing stands to grow pine back should have been paid up front as part of the price of the timber that was sold off at what were bargain-basement prices. It has instead fallen to taxpayers, or in the case of private forests, remedied by selling off the land, what’s left of the trees, or both.

The public, having never been given a realistic price for its timber, is now asked to foot the bill for, at minimum, a hundred years of management, and that’s very optimistic. Short-rotation cropping has proved to be an abject failure. Moreover the seed-stock necessary to generate the best possible forest on a given site – from the cones on the trees that were originally there – have been carted off to the mills. There is no getting back those millennia of evolutionary benefits. The research that describes all of this is well documented.

As for the timber market, it became part of a much broader collapse that has little to do with environmentalism, and everything to do with technology in the 1980s, and then greed and gullibility from the 1990s right into the housing collapse of the 2000s.

The ecological part, the removal of the older forest trees, wasn’t even the biggest factor in the loss of jobs during those decades. That prize goes to increased automation and to the development of an unsustainable housing market built to feed bogus investment schemes, not to meet the needs of real people. The 1980’s saw the cutting of 40% of all the trees that had ever been logged on National Forests but mill jobs continued to disappear thanks to machinery. Then in the 1990s, Wall Street decided to create investments that derived their value from thousands of bundled home loan payments. That fed multi-million dollar bonuses for the suits and made a lot of IRAs look good, but it wasn’t sustainable either.

The skids were greased for the collapse in the last days of the 1990s, when regulation of these derivatives was prohibited in a 200-page amendment slipped into an appropriations bill by Phil Gramm. The resulting frenzy of greed-driven speculation drove home prices to levels never seen till then. As one example, Californians were getting loans for thirteen times their annual income when good real estate professionals use a value of 3 times income to decide whether a buyer can afford a property. That ended and the housing market there collapsed eventually leading to a four and a half year supply unsold. With it went the demand for lumber.

As a long-time reader of the Oregonian, I was just as disappointed by the historical lobotomy the paper seems to have undergone. The forests of the interior West have been subjected to wave after wave of collapse and consolidation. The history of logging in this part of the world is filled with this sort of boom and bust cycle. It’s why we need a diverse economy.

The newspaper’s lack of acquaintance with that boom and bust history is not even the most egregious problem with the editorial. That prize goes to the absurd notion that the public would ever have been given a say on private holdings. Forestland owners are doing what rational actors usually do with their investments, they’re maximizing them. That may mean liquidating the timber when the price is right, and if it can best be done by growing a crop of houses that will be the plan.

Imbuing the environmental movement with god-like powers – while giving the derivatives-crazed notions of Wall Street and the financial shenanigans of it’s acolytes in the timber industry and the larger world of hedge investing a pass – is willful deceit and a failure of journalistic competence. Real-estate investment trusts are just the final chapter in the gradual removal of the public from any say about the health of the forests lands the state was endowed with, both on the wet side and the dry side. That’s what happened, that’s the system that was built. That’s the one any reliable news source would discuss.

Blind to the End Game

The (Forest) Vision Thing

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Logging has always been heavily subsidized in the interior Northwest. That was politically driven and it led us  down the path to overstocked forests. The timber was given away, often below market value let alone at the cost of replacement. That cost is a function of what it takes to grow the next stand. That was never factored in because doing that would have made the timber unsaleable. So the management needed to grow replacement forests has always lagged far behind the desire to keep pushing timber out to the mills.

The natural result is overstocked, and in many cases heavily overstocked, stands that are coming in at hundreds and some times thousands of stems per hectare. That leads to drought-prone soils, and nutrient shortfalls. Fire is the primary means of redress and in lieu of that, insects, so fires suppression hasn’t helped the situation at all.

Speaking of which, insects and those interior forests are so tightly bound they should be considered one biological entity, not two. Spruce budworm, Tussock moth and the Western and Mountain pine beetle are not pests in any sense of the term. Spruce budworm works at the intra-stand level, opening up overstocked forest stands over an 8-10 year period. Tussock moth simply knocks down stands that have encroached onto sites on which they are not suited. It re-sculpts those stands in about three years, probably an adaptation to what we know has been the regular cycling of global temperature over the last 400,000 years. It works at the stand scale. The pine beetle, the most important insect in the Western Hemisphere, will take down all the lodgepole pine for as far as the eye can see, re-setting the clock on those forests. That’s happened in the Canadian Rockies and interior British Columbia over the last 20 years and in many parts of the interior Western US.

Vostok ice-core record, courtesy of AntacticGlaciers.org.

Lodgepole pine only live to be 70-80 years old at which time something has to take them down. We started seriously suppressing fire maybe 100 years ago? I don’t believe the current timeline for lodgepole die-off from the pine beetle is a coincidence.  Moreover if we are experiencing the effects of climate change, that could be one more signal for the beetle to bring it on.

Not enough of that science informed the reaction to those outbreaks, unfortunately. I worked for Forest Service Research  for 26 years and we were the red-haired step-child of the National Forest System. We would write up reports that detailed those relationships only to have many of them ignored. I have an endless supply of stories about that. The key point is this: the only funding available for forest management was from the Knutson-Vandenberg Act – mitigation money for cutting trees. That perverse incentive did exactly what you might imagine, it yoked intelligent management to unprofitable logging, stifling the former and monetizing the latter.

The result, given the excessive drive for that pot-of-gold at the end of the rainbow, was a much darker reality – coal in that rainbow stocking if you like. This story, for example, needs airing. The failure of industrial forestry on the Oregon Coast led to an on-going disaster. That narrative is complicated enough that nobody ever seems ready to write about it. Given the difficult questions it asks about the state of industrial forestry, that’s not surprising, but badly needed.

What’s a forest – and its genes – worth?

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A friend recently wrote up a plea that our state do a better job at managing its school fund. I couldn’t disagree with his logic since the state is mandated to maximize that fund which depends on timber receipts from the state forests. This part of his argument, however, caught my eye. He wrote that
 
“[t]he state itself is a poor manager of commercial timberland”
 
I dug up his email address and wrote him back to expand on that notion. The bad news is that the commercial interests have been even poorer managers of timberland. The story hasn’t gained much traction in the press but that management failure is no secret to the scientific community. The details need an honest airing in a pubic arena as well. Lurking at the center of this management disaster are a set of assumptions that have collapsed completely, bringing into question the model used by the timber industry to manage forest lands. What was once a minor irritant in Christmas tree plantations, the so-called Swiss needle cast – it isn’t Swiss but they first took note of it on imported specimens – has collapsed the growth curve for industrial forestlands in the Coast Range, those with mono-cultured stands of Douglas fir. Now that’s a very broad statement, but the evidence for that collapse is itself very broadly distributed, as can be seen from this map:
 
Swiss Needle Cast Cooperative - 2013 Aerial Survey

Swiss Needle Cast Cooperative 2013 Aerial Survey

That image was taken from the OSU Dept of Forestry’s Swiss Needle Cast Cooperative website. The industry funded cooperative was formed when the outbreak started to cause a serious dent in revenue forecasts. It’s from the 2013 survey of the disease. The outbreak has grown worse over time as can clearly be seen from the mapped history of those surveys. A more detailed synopsis of the cause for the epidemic can be found on that same website:

Disease is most damaging close to the coast, and severe disease has been associated with several climate and topographic variables, including spring leaf wetness from precipitation and fog, mild temperatures in the winter and spring, and low-elevation valleys.  It is believed that the current epidemic is attributable to a variety of factors, particularly the increase in Douglas-fir plantation acreage in coastal areas that were previously dominated by spruce, hemlock and alder and have environmental and site conditions conducive to disease development.  Much of the current research is focused on understanding the impacts of soil and foliage nutrition on swiss needle cast disease development and severity, assessing disease growth impacts, and modeling and mapping the current and projected distribution of disease. (my emphasis)

…which is undoubtedly why ‘…spruce, hemlock and alder…‘ grew there in the first place1. This pattern, let’s call it ecosystemic over-reach, has been repeated on the East side of the state as well. That’s a long story itself, but it also needs airing. You can find some of it here in a paper I wrote 20 years ago.

To my mind these two case-studies are symptomatic of a near-complete failure of industrial forestry, something that will, I believe, become even more evident over the timescale at which forest stands develop, on the order of hundreds of years. The evidence continues to mount as time passes.

What follows is my personal indictment of the timber industry.

It was a mistake to ever work on a margin that had Douglas fir replacing mixed stands. Those stands appeared to ecologically uninformed eyes, something that’s inexcusable for an industry who’s business should be all about ecology,  to be too slow-growing to deliver the expected profit. Convinced they could force those forest lands into new modes of production, they instead birthed a slow-growing disaster born of arrogance and short-term thinking. The idea that stands could be worked at that margin for increased yield by planting those mono-cultures is the core of the problem, and a clear reflection of a terrible business model, one that neglected crucial information. That information was readily available to them, but it came from sources outside their narrow blinkered view of the forest world. Those blinkers are derived directly from that arrogance. That was all too obvious from my first days in Oregon in the late 1970s.

Having worked with biologists in my prior life with the early EPA in Las Vegas, I was quick to comment on a policy that had all but eliminated almost every vestige of the older forest. That forest wasn’t just a show-piece I wrote, it contained the very genetic resources necessary to deal with any future problems – problems of exactly the magnitude presented by Swiss needle cast it turns out. Those were my comments to the Siuslaw NF, asking that those genetic resources be preserved. That’s just an outsider feeding unwanted white noise into the system after all. How about the insiders?

Years ago, one of the Forest Service’s stellar research sivliculturalists wrote up a brilliant synthesis about his research work: Nitrogen, Corn and Forest Genetics. He hammered home in no uncertain terms the fallacies behind an agricultural strategy for forest lands and foretold the failure of that strategy, pointing out the near-template like fit of the best adapted seeds to the landscape from which they were gathered.

None of it cut any ice. The political agents of the timber industry were deeply embedded in every advisory board the state had, something I learned first hand as background for my initial foray into the state as a contractor representative. They also had the Oregon Congressional delegation, which had been catering to the industry since the earliest days, safely in tow. That insured that any such scientific mumbo-jumbo would be ignored. The industry would simply engineer a new forest, ecology aside. The Forest Service decided to cut just about all of those older forests, that arrogance spreading like a stain across the policy landscape, one which had been carefully prepared to receive it. Private timber land owners did cutover all of their forestlands, leaving them with an empty gene pool from which to rejuvenate those hard hit stands.

Here’s my personal economic mantra: greed is short-term self-interest, morality long-term self-interest. The stark difference between those two emotional polar-opposites, is a simple function of the time and depth we’re willing to invest our planning horizon with. That’s something many economists have somehow lost in both their qualitative and quantitative analyses. It’s something they need to recover if we expect to stick it out for a while, a while that would include that moral future. It’s one that, I might add, would actually have room for all the genetic resources our forests have to offer, the ones we have so casually discarded in our quest for short-term profit.

1 In the 2002 publication Forest and Stream Management in the Oregon Coast Range, the authors have this to say

Douglas-fir, which is the foundation of timber management throughout most of the Coast Range, will become a less important timber species in moist areas of the western slopes as Swiss needle cast (Phaeocryptopus gaumannii) drastically reduces growth rates in these areas… Hemlock, on the other hand, is resistant to the disease and has relatively good growth rates in these areas.

Sitka Spruce

Sitka spruce in an uncut Oregon coastal forest

Forest for the ages

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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.

Old-growth Ponderosa pine
Old-growth Ponderosa pine: USFS Region 5 / CC BY (https://creativecommons.org/licenses/by/2.0)

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.

The Lost Forest Research Natural Area, Central Oregon
The Lost Forest can be found… miles from the drying shadow of the Cascade Range.

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.

US Forest Service, Rocky Mountain Research Station

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).

Running on climate time

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I recently had a chance to watch a video recorded as part of the series on Adapting to Climate Change a course for land managers developed by the US Forest Service and it was excellent. It brought to mind an article I wrote years ago, in 1994 to be exact though it wasn’t published till 1997 in the Fall issue of the late great Wild Earth.

It was inspired by the work that was done coring the Greenland ice sheet, a real eye opener for me. During the last glaciation the planet would regularly transition from an average temperature that’s a few degrees warmer than now to a few degrees cooler in as little as 10, and maybe fewer, years. You can get a hint of these gyrations from the chart shown below:

Temperature proxy from ice cores
Temperature proxy from ice cores for the last 140,000 years (Wikipedia).

That’s an almost incomprehensible shift in the planet’s energy budget and it would have had a dramatic effect on the climate and the vegetation everywhere. This has huge implications for everything we think we know about forest, grassland, and desert ecosystems in the West. Yet those implications have, to this day, barely been discussed.

Here’s one of them: the gene pool of our western conifers has to contain the necessary diversity to deal with rapid climate change and we need to incorporate that into our thinking. That’s not an excuse for doing nothing. The potential social impact alone is enormous. It’s simply a statement of fact.

Take Ponderosa pine as one example. In the Southwest it has such a tightly bound relationship with Abert’s squirrel, that the only thing that critter sleeps in is pine-needle beds, and just about the only thing it eats are Ponderosa pine seeds. When I mentioned this years ago to a British geneticist, he said that probably represented at least 10 million years of co-evolution. If Ponderosa’s been a part of the Western ecosystem that long, the species has surely been through dozens and dozens of episodes of rapid climate change. It’s still around (and it’s also fast on its metaphorical feet as evidence has shown) so it has the diversity to make it thorough those rapid shifts.

At the same time as the results were coming in from the ice-sheet cores, we were just coming out of a spruce budworm outbreak in the Blue Mountains of Oregon. The forests were making a remarkable recovery after that episode. But the reaction to the 8+ year outbreak was very revealing. It seemed to induce a form of ecological insanity in otherwise intelligent people. The budworm was imbued with demonic powers, a satanic force out to do us in. This wasn’t science as I thought I new it. The only people who made any sense at the time were entomologists such as Boyd Wickman. He and the others in his research unit kept saying that outbreaks have a way of ending quite quickly, and that the forest can recover just as quickly when it does. Their voices were subdued and rational, and just about completely drowned out by calls to log everything in sight.

I’m a mathematician by training and it smacked of the sort of pejorative language that discipline was riven with before “negative” and “imaginary” numbers were put on a solid footing. It’s also the same sort of language I heard used about one of the most versatile hardwood species in the world, red alder, when I first moved to the NW in the late 70s. “Professional” foresters called it a weed and insisted it had to be poisoned out of existence. Later I found out that it had such a tightly-bound relationship with nitrogen-fixing bacteria that it might as well be a legume. It’s so valuable for rehabilitating logged over lands that it gets star billing in this amazing book, one of only two species (Neem is the other) that has more than a single page entry. That told me all I wanted to know. Forestry, at least at that time (1978), was certainly not a science and it seemed to me barely an art.

So I wrote the article in reaction to the coring of the ice-sheet, and the evidence I could see on my own at the end of the budworm outbreak. It started as a letter to a good friend, then later I expanded it as a piece for Wild Earth.

My own opinion is that the budworm and its host species are so tightly intertwined that they’re really not separable parts of the ecosystem. You take one, you get the other. That’s even truer for the mountain pine beetle and Lodgepole pine. The 17+ million hectare pine beetle outbreak, that draped itself like a multi-colored cloak across the mountain forests of Alberta and British Columbia in Canada, is a very dramatic example of the phenomenon I outlined in my article: a false climate signal brought on by years of fire suppression that leads to an eventual re-balancing of the system. In the case of Lodgepole, that’s probably exacerbated by real climate change driving the ecosystem the other way, further northward in the Canadian Rockies.

These ideas now seem to be gaining currency and that’s long overdue.

And further to the South…

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So where else should we look for climatic analogs to the ecosystems of the Western US? Head north, from Antarctica into the Pacific, staying close to the South American coast. To the east, the Andes rise out of Tierra del Fuego, building a very effective barrier to moisture for thousands of  kilometers. Since the earth mirrors the atmospheric circulation on both sides of the equator, this means that the pattern of vegetation – from rainforest, to chapparal, to desert and then into the tropics in North America – repeats in reverse to the South. After the tropical belt comes the Atacama desert, then the Chilean Mattoral, and then the Valdivian rainforest, a twin to its North American counterpart in Cascadia.

Compounding the eerie similarity is the geology. Just as in Cascadia, a subduction zone lies off the coast of Chile, with the Nazca plate diving under the South American, periodically firing off massive earthquakes as it does. Jammed under the earth’s crust as they are, both plates send enormous plumes of melted rock to the surface where they express themselves as chains of spectacular volcanoes, one each for the Americas North and South.

Head to the lee side, and the drop out of the Andes takes you through the transition zone of dry forests and prairies. It’s no great surprise that Ponderosa pine, the iconic forest tree of the interior West, finds a home on degraded range in those borderlands. Travel further and you’re in the Patagonian steppe, indistinguishable to the untrained eye from the Great Basin.

Central Asia as Surrogate

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Years ago, at the Forestry and Range Lab where I worked, we hosted Alexander Isaev, then Forest Minister of the old Soviet Union. He’d been appointed to the position because, as he told me through his interpreter, he’d “complained so much that Gorbachev said ‘you take the job'”. The very first thing I’d questioned him about was his impression of traveling through Oregon. He’d just flown in from the other side of the Cascades the previous evening. That thin strip of well-watered forest usually draws all the attention from visitors, especially the lush temperate rain-forest in the coastal mountains. A world-away from the dry interior, it edges its way southward along the Pacific Coast down from British Columbia, finally tapering to a width of of no more than a few miles populated by redwood stragglers tucked away on isolated mountain peaks and in the hidden canyons fingering into Mediterranean California. I was expecting he’d reflect on that world. Instead he paused for a few seconds and looked up and away, into his past it seems. When he woke that morning and looked out his window, he thought of his first posting as a young forester, to Samarkand.

That’s a clue, and a good one. Much of Central Asia has a similar climate to the American West. I remember eagerly leafing through Heinrich Walter’s Climate Diagram World Atlas many years ago (some of which have now found their way online), quickly locating analogs to the climate of the region we’d moved to in Northeast Oregon. These analogs included places like Van, Turkey and Tashkent, Uzbekistan.

The difference is that such a vast place has been host to any number of nomadic tribes roaming from Europe to Asia and back, a human wave of aggregate demand on the land that was just as vast in its effects. We’ve all heard the stories of ransack, rape, and pillage. Notice that those are all human-centered observations. What usually gets lost in the telling is the ecological history of the Eurasian landmass.

Any number of  dramatic mountains and highlands  should, and at one time did, host thickly forested montane ecosystems. Some, such as the Anatolian plateau, the Lebanon, and anti-Lebanon ranges, and the Zagros mountains have been deprived of most of their forest cover.  Too often that has meant the soil that held them in place and nourished them has vanished as well. First the superstructure of trees that ameliorated the above-ground climate and tempered the erosive force of water was removed. Then the substrate that acted not just as a physical prop, but which hosted the nutrients needed to feed the trees, and likely the micro-organisms needed to produce future forest stands as well, was carried off by wind and water.

Other mountain systems have been subjected to an ever-retreating treeline which has pushed those ecosystems further and further up their heights. The Caucasus, the Tien-Shan, and other spectacular ranges have seen their share of human activity and the impact has been significant.

Rainshadow…

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What makes the American West different? My guess is the length of time it’s been subject to dense human settlement and the serendipitous arrival of those settlers when fuel sources other than wood were just becoming available.

There are at least a few parts of the world that have similar climate patterns and vegetation, though the very size of the ecosystem in Western North America insures that there won’t be many worldwide. The mountain blocks that divide wet from dry, or at the very least semi-arid from arid, stretch from British Columbia down through much of Mexico with only a few gaps in between. The coast  mountains of BC, the Cascade mountains in the Northwestern United States, the Sierra Nevada down through California extending southward to the coastal ranges of California, and the massive Sierra Madre Occidental in Mexico all cut the interior off from Pacific storm systems that might otherwise provide moisture to the drylands. At it’s widest extent, crest to crest from Mt. Whitney to the Front Range in Colorado, the dry gap is easily 900 miles across while north to south, it encompasses a few thousand miles at the very least

To get an idea of how extensive it is, we can use a proxy. Ponderosa Pine is just such a stand-in. It’s a species that conveniently fringes the dry interior of the western continent, separating the xeric domain from the wetter ecosystems that lead up to the adjacent high country, if any.

As befits good tree-people, the U. S. Forest Service, in the person of E. L. Little, Jr, lovingly built up an atlas of maps showing the geographic range of all the species in the United States. That was in the 1970’s. I picked up my copy of Volume I years ago at a yard sale. The cover was a bit charred from fire, appropriately enough. Otherwise the volume was completely intact and in very good condition including the delicate transparent overlays threaded through with solid isopleths for rainfall, temperature, and other important environmental variables. These overlays chart the chromosomal DNA for our North American landscapes! The range maps in their entirety have been digitized and are available on the Internet courtesy of the USFS. If you care about such things it’s easy to lose yourself at the site for hours.

Climate diagrams are a great way to draw a bead on similar climatic patterns. These patterns largely determine the ecophysiology of a place and the kind of vegetation that can grow there. Places with comparable climate often host similar plant communities, communities that have developed on convergent evolutionary pathways. The look of these communities can be startling in their visual coincidence, even when those communities are composed of different genera. For example, the Ethiopian desert hosts a community with euphorbia, aloe, and acacia that mirror the plant communities of Sonoran Arizona, with its cactus, yucca, and mesquite.