ONE TOWN SQUARE: at the intersection of peak oil, climate change, and land use

A couple of articles point out how humans are profoundly altering both terrestrial and marine ecosystems around the globe.

An increasing percentage of greenhouse gas emissions is a result of deforestation and forest degradation. The current split of greenhouse gas contribution is 80/20, between energy sources and deforestation. However, that percentage may alter if we don’t stop chopping down trees.

Deforestation means the complete demolition of forests. Forest degradation means that the larger trees are chopped for timber, leaving the forest with only lesser trees. The three countries producing the most emissions through deforestation and forest degradation are Indonesia with 35% of such emissions, Brazil with 19%, and Malaysia with 10%.

Population growth and development are driving deforestation. Population growth brings demands for more housing and commodities such as timber, paper and agricultural goods. So forests are flattened for residential space or farm plantations and  the wood is harvested for timber or wood by-products. Oil palm plantations in Indonesia and Malaysia are major culprits. Both countries earn much of their GDP from exports of palm oil, which is used in food, biofuels and cosmetic products. 70% of Indonesia’s oil palm plantations were originally forests.

Carbon emissions – whether from the burning of fossil fuels or land use changes -  are in turn changing seawater chemistry, causing ocean acidification. Currently, the upper layer of seawater averages 8.10 on the pH scale, which goes from 14 to 0 and describes the increasing concentration of hydrogen ions. The pH scale works logarithmically, so 7 means 10 times more ions than 8. Plain water, defined as neutral, is 7, and lower numbers indicate increasingly strong acids and larger numbers of hydrogen ions. Since the beginning of the industrial age, the seawater pH has slipped about 0.11 of a pH unit. By the end of this century, the upper 100 meters or so of ocean water will be more acidic than at any time during the past 20 million years.

This shift in seawater chemistry will affect seaweed, corals, fish, and other marine life. Marine species from corals to snails to floating dots of life called coccolithophores create structures of calcium carbonate. A CO₂ boost makes this job harder. A key ingredient in making calcium carbonate is the carbonate ion, CO₃^–2. Hydrogen ions react with the carbonate ions in the water, thus making them unavailable to calcifiers such as corals building reefs. The intricate crags and crevices of reefs shelter much of the biodiversity of oceans, perhaps a million species. Without complex reef habitats built by corals, it will be a simpler ocean. So by changing the oceans’ chemistry and biology, we are essentially creating new oceans.

If the CO₂ in the atmosphere were to be stabilized at its current concentration of 380 ppm, most of the world’s current reefs would survive more or less intact. If atmospheric CO₂ were to reach 450-500 ppm, large swaths of ocean once hospitable to reefs would become so starved of carbonate that more and more corals in the upper 100 meters or so of water could no longer add to their skeletons, and the rich habitat offered by coral reefs would dwindle. Over 500 ppm, all that would be left is “slimy rocks.”

And that prospect leaves out the effects of heat. Depending on the coral species and the place, 3 to 4 weeks of temperatures a degree or two Celsius above current summer peaks can “bleach” a reef, turning it into a spooky white sculpture of itself. This bleaching comes from the breakdown of the partnership between warm-water, soft-bodied corals and their colorful live-in algae, or zooxanthellae. They photosynthesize, and the host corals take a share of the lunch. Sometimes the partners get together again after a bleaching break-up, but prolonged absence of zooxanthellae kills a shallow-water coral.