Archive for the ‘other’ Category

Our native forest

8 February 2016

I spent Saturday in Napa Valley on a field trip with the Northern California Geological Society, visiting the ultrapremium Promontory vineyards west of Yountville and the merely superpremium vineyards of Harlan Estate west of Oakville.

High-end wine is a culture obsessed with the character of land, and Bill Harlan talked a lot about his land as we tasted the 2009 releases from both sites. What struck me most was his emphasis on the forest around the vineyards. Both properties are enclaves of vineyards in a forested setting. This view of woods-encircled vines is from the top of Promontory.

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Harlan spoke of airs and influences while, given my recent reading, I thought of wild yeasts and soil microbiomes. I also thought of Oakland’s woods, which have been on my mind lately as I’ve explored the Leona hills.

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To some Oaklanders, all trees are good trees. To me, the oak forest is what belongs here, and eucalypts should be exterminated from our wild lands. I’ll spell out several reasons, mostly familiar, plus a new one about living in Anthropocene time. But first, a clump of oaks in the Leona hills.

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History: Once our oaks were the basis of a thriving native economy, and their acorns are still here in abundance for true locavores. Eucalypts were planted in our hills in a failed attempt to make a killing in timber. The poet Joaquin Miller, spellbound by a Victorian ideal of Arcadia, covered his grassy Hights with thousands more. Neither wave of tree-planting was done responsibly. We owe that legacy of heedlessness the same respect we owe pampas grass, French broom, foxtail grass and other pest species. Here’s a mono-stand near the Caldecott Tunnel.

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Aesthetics: Our native oaks hug the hills in fleecy blankets; eucalypts hide them in scraggly tufts. Compare the two types of forest, side by side at Lake Chabot. The very air is different.

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Accessibility: In my search for rocks, I go off trail and across country. Eucalyptus country is typically impassible, the footing noisy and slippery. Oak country is typically parklike and quiet, like this grove in the Leona hills — although it’s friendlier to poison oak, I’ll give you that.

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Ecology: Oaks make food and mulch; eucalypts make trash.

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The Anthropocene: The future’s climate is up to us. It’s vital that we pull CO2 out of the air. Trees are touted for doing that, but planting and managing forests is a sophisticated practice we’re just beginning to understand. Forests are more than just groves of fixed carbon. By far the majority of a forest’s carbon is in its soil, not above the ground.

A newly published study argues that more than two centuries of reforesting the European landscape hasn’t made a lick of difference to its CO2 balance. Because the new forests were managed for timber, the wrong kind of trees were subsidized.

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Luckily, we don’t harvest timber in Oakland any more, so we can do things the right way. That means nurturing the biomes that suit the region: native oaks, redwood, chapparal and coastal wetland. Their intricate webs of underground organisms, tuned to our rocks and climate over thousands of years, soak up carbon better than any other strategy.

Well-chosen eucalypts are splendid specimen trees, but they should be phased out in the wild. If we feed our wildland soils correctly, Oakland can do its share to fight global warming. And it will be better in all the ways I’ve mentioned.

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Restoring our land will take time, sustained funding and the same dedication that Bill Harlan gives his vineyards. If we take our ownership of Oakland’s land seriously, we can’t slack.

Two lessons about floods

19 October 2015

As we anticipate the strong possibility of heavy El Niño rains, my attention will be on Oakland’s streams this winter. Last week parts of southern California were hit by “thousand-year” rainfall events, cloudbursts that washed thick sheets of mud over roads and properties. We can expect such things here too, in any given thousand-year period.

Arroyo Viejo, the stream that crosses Knowland Park, offers two lessons about floods. The scene below is at the northern edge of the park, looking upstream: a streambed piled with boulders, some as large as sofas. (All photos 800 px)

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Notice: these rocks have been tumbled by the stream. How much water would it take to do that? Let’s make a rough, arm-waving estimate.

The rainfall in last week’s cloudburst was almost 4 inches in one hour. Had it fallen on the watershed of Arroyo Viejo above this point — say, half a square kilometer — it would represent an input of roughly 30 cubic meters of rainwater every second.

Picture in your mind that volume of water — no, it would be mud and therefore that much greater — funnelled through this narrow valley. Do a little geometry and it’s easy to see the floodwater would be well above the tops of the boulders.

Hidden in plain sight in this photo, then, is a single hour of tumult that might have happened a thousand years ago or five hundered years ago — or perhaps during the dreadful winter of 1861-62, when it rained for 43 straight days and much of the Central Valley became a lake.

The lesson is that most of geology’s hard work gets done in rare spurts of extraordinary activity.

Okay, the second lesson is hidden in these rocks. All of them, like this boulder as tall as me, are made of conglomerate.

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These rocks, assigned to the Knoxville Formation of Late Jurassic to Early Cretaceous age, were laid down by ancient floods in a nearshore or terrestrial setting. I’ll show you three different specimens. Notice the large clasts and the fine-grained matrix that surrounds them.

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This boulder displays a wide range of clast sizes. It was probably laid down by what’s called a hyperpycnal flow, a slurry of sediment that carries everything along with it. We’ve watched them happen offshore in Monterey Canyon. Here’s another example.

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Instead of an underwater landslide, as seen in the first specimen, this represents something gentler and more organized, like a mudflow, or like the mudslides we saw in the news. The clasts are aligned with the current that carried them here.

The key observation in both cases is that the large clasts are floating in the matrix. In geologist’s terms, they are matrix-supported conglomerates.

Then we have this.

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Here’s a beautiful clast-supported conglomerate. It represents a clean bed of well-rounded cobbles, all touching each other, like you’d see in a rushing stream or a rocky beach, nicely infiltrated with clean silt or clay after it was laid down.

None of these stones were made by ordinary sediment wafting down streams during ordinary rainy seasons. They were assembled by floods of all sizes.

Deep time and Deep East

28 September 2015

The deepest part of Deep East Oakland, at the south end of the alphabet streets, is a neighborhood that shows its age. First laid out and developed almost a century ago, it was a desirable locale, with good transportation, fresh air, a warm climate and excellent soil, plus nice views of the hills.

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The neighborhood retains modest homes from a wide range of 20th-century styles.

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There are also front-yard fences everywhere, signs of a more recent stage of the local culture.

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So why do I bring up deep time when I think about Deep East? “Deep time,” the wonderful term first used by John McPhee in Basin and Range, is geology’s great insight that Earth history is essentially infinite. Put another way, by paying careful attention to the geology of the present-day landscape, we can deduce many facts about the deep past. With that knowledge we can visualize ancient worlds with different landscapes, superimposed on our own. From those visions, informed by geologic fact, we can see light shed upon even earlier landscapes and worlds, and there seems to be no limit. This is similar to how astronomers know the universe — deep space — in ever-greater detail as our instruments improve.

We also learn that even while the landscape is far older than the human presence in it, some parts of it are old and some are quite young in geologic terms. The young features took their place by erasing something older. The ongoing processes of geology — uplift, erosion, consolidation, disintegration — lead to a pleasantly mixed landscape just as the ongoing processes of humanity — birth, death, migration, commerce — lead to neighborhoods like Deep East. Landscapes and neighborhoods both are always changing, and each day’s present is a snapshot never to be repeated.

The more I learn how much Oakland has changed and how many ways it can change, the more precious becomes the present. Some day, earthquake or rising sea level or century-long drought will wipe most of our present away. So as I walk around this town I always know that the panorama has a big label on it that reads “Before.”

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What the “After” scene will look like is to be determined. We know that by personal initiative and supportive policies, historic properties can be safeguarded for the future, with the hope of maintaining and reviving what’s precious about a neighborhood.

The same is true for Oakland. The same is true for the Earth we live on. Spread the word and enjoy today.


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