Saturday, March 06, 2010

Climate change, trees and your sinking home

If the Earth were warming smoothly everywhere, then we would expect to see the gradual migration of ecosystems. Iowa would migrate into Minnesota, and the Arctic would migrate into outer space.

Of course the Earth is not warming smoothly everywhere. It's warming on the average, but on the human level things will be messy. If greenhouse gases, particulates and other side-effects of humanity stabilize (a big if, unfortunately) then we might eventually return to the relatively predictable weather cycles of recent millenia. During the next century, however, the weather-cycles are likely to be turbulent.

What does turbulence and year-to-year micro-climate unpredictability mean to ecosystems? I've not read anything on this topic, and a quick gSearch found only some 2009 conference proceedings on marine ecosystems. I'm guessing we'll start reading about this over the next year, so this is your prologue.

As an uninformed guess, I presume this weather/climate turbulence will favor organisms that adapt rapidly to change. That would normally include humans, but we saturate most every ecosystem and, given our weaponry and limited judgment, we're likely to react to turbulence with devastating warfare.

Humans and their canine parasites/symbiotes aside, one would expect organisms with high mutation rates and short life cycles to do well. So that would include insects, bacteria, grasses, fungi and so on - including many things we consider "pests". On the other hand, we might expect trees to do quite badly in the near term. They could do fine in the post-turbulent future, but they don't seem likely to respond well to unpredictability.

Which brings us to your soon to be sinking home. If you were to look down at my neighborhood in St Paul Minnesota in July of 1999 you would have had a hard time seeing the houses. All you'd have seen would be trees. That's not so now. Pests and fungi have devastated our canopy. (This is not entirely due to climate change -- the emerald ash borer's range extension was assisted by human transportation. So our treescape is a premonition of what climate change may bring, even though we have assumed Iowa's old climate.)

How does losing trees impact your home? Well, we ain't called the "land of 10,000 lakes" for nothing. Twin Cities water lies close to the top of our clay soils. In this setting losing trees can have unanticipated consequences (emphases mine) ...
Shifting Soil Is Threat to a House’s Foundation -

... Data from the National Oceanic and Atmospheric Association indicates that since the 1990s there has been an accelerating trend nationwide toward more extended dry periods followed by downpours. Whether due to random climate patterns or global warming, the swings between hot and dry weather and severe rain or snow have profoundly affected soil underneath buildings.

Clay soils, like those beneath the houses of Mr. Derse and Ms. Wilson, shrink during droughts and swell during floods, causing structures to bob. And because sandier soil loses its adhesive properties in dry conditions, it pulls away from foundations. Heavy rains cause it to shift or just collapse beneath structures. With both kinds of soil, such sinking, called subsidence, usually happens gradually, said Randall Orndorff, a geologist with the United States Geologic Survey. But, he said, “swinging from very wet to extremely dry weather like we’ve been seeing lately in many parts of the country may be accelerating the effect.”...

... Subsidence is not covered by most homeowners’ insurance policies in the United States, unlike in Britain, where the increasing number of homeowners’ claims due to foundation failure prompted the Charter Insurance Institute, an industry trade group, to issue a dire warning about the financial drain in its 2009 report, “Coping with Climate Change: Risks and Opportunities for Insurers.”
“The question we need to ask is, are we building to cope with the enhanced weather events related to climate change,” said Brenda Ekwurzel, a climate scientist with the Union of Concerned Scientists, a nonprofit group advocating science-based solutions to environmental and health issues. “It’s obvious that we need to look at changing building codes worldwide to deal with this.”...

... Fixing a failed foundation usually involves hiring a foundation repair company to install cement or steel piers around the perimeter of the house’s slab or near its existing piers if it is a pier and beam foundation. Once in place, hydraulic jacks lift and level the house and transfer its weight to the new supports. The cost depends on the severity of the problem but generally runs about $1,000 to $2,000 per pier, which should include a lifetime transferable warranty.

“It’s amazing to watch your house get jacked up like that,” said Miguel Rivera, a designer of heating and air-conditioning systems, who had to pay $13,000 to have his 60-year-old house in West Orange, N.J., shored up in January. “It’s just immediate. You’re like, whoa, up it goes.”

His dining room began separating from the rest of his house about five years ago after repeated heavy rains shifted the earth beneath it. The problem was made worse when he removed a nearby tree, which was probably siphoning off excess water and providing structure to the soil beneath his house.

“It often happens that you upset the moisture and structural balance when you knock down or tear out trees,” said Mr. Lourie, the geotechnical engineer, adding that planting trees too close to the house can be harmful. “Plant them at least half their mature height away from the house.”

Landscaping should, as a rule, be installed so that water slopes away from the house and gutters should discharge at least five feet from the house to avoid oversaturating the soil. During droughts, experts recommend placing soaker hoses around the perimeter of the house and turning them on for 30 minutes a day. “The idea is to maintain a constant amount of moisture in the soil,” said Tom Witherspoon, a foundation engineer in Dallas. “If you can do that, your house will never move.”...

... Engineering and structural-repair professionals say it is relatively easy to spot foundation problems in structures that are more than 10 years old. If you are considering buying a house, look for patched-over cracks in brick or drywall and doors that have been planed. Also notice if there are cracks in sidewalks and streets in the neighborhood.

... problematic areas like the Southeast, Southwest, Midwest and coastal states...
I like the last sentence. Why don't they just tell us what state doesn't have a problem? New Mexico?

So what should those of living in "the Southeast, Southwest, Midwest and coastal states" do? Many will have to budget for serious foundation work, and foundation/soil assessments will change property values (and thus property taxes). I'm most interested in whether we can use tree planting to manage a high and fungible water table. What trees do best at pulling up moisture in wet times, yet are likely to be pest resistant (assuming we provide the water in dry summers -- in Minnesota this is feasible)? How well does this work in reality?

I expect we'll learn a lot more on this topic over the next two years.

Update 4/7/2010: Some real science to complement my tree speculations ...
Tree-mendous - Opinionator Blog -
... being a tree has challenges ... longevity itself creates difficulties. In the course of centuries, situations change: droughts and fires may come and go, soil may erode, water tables may rise and fall. Worse, other organisms — especially enemies — can evolve far faster, because they can go through hundreds of generations during the tree’s life. How can trees avoid succumbing to diseases? Especially as they don’t have an immune system like ours: you can graft tissue from one tree to that of another (think apples and olives) without the kind of rejection that a mammal would experience. Part of the answer may be that many trees have evolved associations with other, fast-evolving organisms, like fungi and ants, that can protect them to some extent.

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