Running on climate time

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’s 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 corings, 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 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 perjorative 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 seperable when I think of the ecosystem. That’s even more true for the mountain pine beetle and Lodgepole pine. The current beetle 17+ million hectare outbreak, draped 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 supression that leads to an eventual rebalancing of the system. In the case of Lodgepole, that’s probably exacerbated by real climate change driving the ecosystem the other way, northward along the Rocky Mountains.

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


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 USGS at the above link. 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 looks for all the world like Sonoran Arizona, with its cactus, yucca, and mesquite.