Geomorphologist David Montgomery spoke about "the living skin of the Earth that is the foundation for all life on the continents" -- soil. We tend to take soil for granted, he said, but we can actually run out of it. Soil exhaustion brought about the end of prior civilizations, Montgomery explained, noting that "the way those societies treated their land in the end shaped their history."

Europeans began running out of 'vacant land' in the late 1600s and people looked to the New World for the opportunity to acquire their own piece of earth, he said. Montgomery blamed colonial agriculture for the significant decline of soil in the United States. As an example, he pointed to tobacco farming, which not only caused substantial soil loss but also quickly depleted the soil of vital nutrients. After four or five years a tobacco field was not as productive, so the crop would be moved to a new parcel, Montgomery added.

Modern farming practices, the rush to biofuels, and high erosion rates continue to jeopardize the agricultural future of the planet. According to Montgomery, we are losing agricultural soils at a rate of about a millimeter a year -- much faster than they can be formed. Montgomery called for soil conservation measures as well as outlined the practice of biochar. Putting charcoal into soil increases organic matter, allows it to hold more water, and sequesters carbon, he remarked. Montgomery also touched on the vulnerability of hybrid crops, ancient Roman farming techniques, challenges to China's food production, and the concept of urban agriculture.

Lileks' UFO Sighting

In the first hour, columnist James Lileks shared details from his recent UFO sighting. Lileks said he had stepped out to smoke a cigar Thursday night when he looked into the sky and saw a "bright streak of light, incredibly fast... going from east to west, jiggling a little bit." The object vanished a moment later, he noted. Lileks said he does not think the object was a meteor or the International Space Station, as it was traveling horizontally very low in the sky. Check out Lileks' own account of the experience at his blog, The Bleat.