Poor farming practices have degraded the world's soils causing them to release carbon that should have stayed in the soil. In the past 150 years soils have released twice as much carbon as fuel burning. Improved farming methods could quickly rebuild degraded land and store enough carbon to offset the damage already done by fuel burning. Dr Rattan Lal of Ohio State University, a leading expert on soil carbon, estimates that the potential of economical carbon sequestration in world soils may be .65 billion to 1.1 billion tons per year for the next 50 years. This is enough to draw down atmospheric CO2 by 50 ppm by 2100. This is a one-time opportunity, however. We must ultimately stop burning fossil fuels.
Man has already degraded about five billion acres of land on the planet by misguided farming practices and overgrazing. In fact, many of the world's deserts were once rich land. Desertification from overgrazing, plowing and growing annual crops has greatly reduced the carbon retained in the earth's soils. Many of our deserts started as forests that were cut or burned down to clear the land and then ruined by overgrazing. If we could reclaim these ruined lands we could restore the carbon balance of our planet.
We have only recently begun to understand the destructive effects of plowing and grazing. The delicate surface crust is an almost invisible biotic network of algae, cyanobacteria and lichens that hold the soil together with tiny filaments. This thin crust takes in an amazing amount of CO2 by photosynthesis and also fixes the nitrogen in the air to a form usable by plants. Tilling the soil breaks up and buries the biotic crust, stopping photosynthesis.
The dust bowl in Oklahoma in the 1930s was an example of the bad effects of plowing the land. Wind and erosion almost turned that once-rich grassland into a desert. In China and Africa the sand dunes have been advancing southward, turning more and more land into sterile deserts. Dust storms in the Gobi desert often block the sun in Beijing and many Saharan dust storms ultimately evolve into the hurricanes in the Gulf of Mexico.
One very encouraging project in China has restored a desert community and given it a source of revenue growing sand willow for making wood planks. This experiment was so successful that the restored area is growing rapidly as more individuals plant sand willow as a source of income. Even more exciting, is the plan to build hybrid solar power plants in the area that will use the sand willow as biomass to feed boilers when the sun doesn't shine. Esolar will provide heliostats and a solar tower for generating solar power in the daytime. The same turbines will be driven at night by steam, generated by burning the sand willow. A total of two gigawatts of these hybrid power plants are planned.
The sand willow matures in only three years and quickly regrows when cut. Villagers sell sand willow timber to plank companies for $30/ton. This economic boom has driven more and more plantings which are greening of the desert. Once a beachhead is established, the local micro climate is changed. Trees provide shade and shelter from the desert winds. Ultimately moisture brings clouds and increases in rainfall. A whole new ecosystem evolves.
Carbon credits could drive this kind of renaissance even faster. It is very important that we develop inexpensive soil carbon monitoring systems so that such important changes in land use can be rewarded. Farmers are already receiving millions of dollars for no-till farming in the U.S. but some have challenged their legitimacy as being "non-additional." Hopefully, projects with multiple benefits will not be deprived of the carbon credits that could drive the fast progress we need.
A "green wall" project has been proposed by the UN that will plant trees along a 7000 km strip on the current southern edge of the Sahara desert. It is floundering now for lack of money but carbon credits for land restoration could restore it to health.
One of the biggest challenges is re-educating people in degraded areas to keep them from turning these areas back into a desert. Grazing goats and sheep were practical only when population density was much less than it is today. Under crowded conditions animal hooves quickly trample the soil crust. Denuded plant life soon leads to erosion and desertification. Goats and sheep are particularly destructive as they pull up vegetation by the roots. Too much of our agriculture has been dedicated to feeding animals, which is inefficient at best. It takes 15 pounds of grain to produce one pound of beefsteak. Fish, being cold blooded, are much more efficient. They eat as little as two pounds per pound of meat.
The "green revolution" doubled cereal production between 1961 and 1985. Unfortunately, much of the increase was based on use of cheap fossil fuels to make fertilizers, pesticides and herbicides and to irrigate and cultivate the land. The energy content of food has reached frightening levels. Worse yet, the whole philosophy of this movement treats nature as an enemy to be conquered. Other plants, insects and microbes are simply poisoned.
Unfortunately, the result of all of this has been degraded soils that need even more chemicals. Good healthy soil can hold three times more carbon than the plants themselves, mostly in the form of humus, bacteria, algae and other organic matter. The University of Illinois has maintained corn-growing test plots for over 100 years. Since 1955 synthetic nitrogen fertilization has been applied, which contained 90-124 tons of carbon per acre. Today, all of that residue has disappeared into the atmosphere adding to global warming and there has been a decrease in soil carbon of 4.9 tons per acre.
Today, there is a healthy revival of permaculture principles that work with nature instead of against it. Annual crops only do photosynthesis during the growing season, leaving bare dirt the rest of the year. By growing perennials, the root mass and the biotic community can grow steadily larger year after year instead of starting from scratch. Roots go deeper and deeper with each season, increasing drought resistance. Yearlong Green Farming maximizes carbon storage in the soil by keeping soil covered with greenery all year long. The world's soils hold three times as much carbon as the atmosphere and four times as much as all of the plants in the world. A large part of the carbon storage is in the biotic soil community and humus, which forms only when the community is kept intact. Restoration experiments in Australia found that conventional cropping practices had reduced soil carbon to half to one third of original levels.
Biomass can be grown from perennial grasses harvested regularly like a lawn that is repeatedly mowed. This allows undisturbed roots to continue to grow larger every year. Symbiotic fungi called mycorrhizae form an association with the roots, which can increase their efficiency by a factor of ten. They are powered by the grasses' metabolism but pay back by creating nitrogen and collecting nutrients. By putting rows or clumps of perennial grasses in fields of other crops, yield can be increased while collecting carbon credits. In some cases 8 tons of CO2 stored per acre per year have been recorded with virtually no biomass inputs. The more the soil has been degraded, the easier it is to earn credits with changes that store significant carbon. A recent study by Stanford University's Carnegie Institution identified 1.8 million square miles of abandoned farmland worldwide.
Heavy use of chemical fertilizers is unnecessary if the soil's crust is kept intact. Even in barren deserts specialized cyanobacteria on the very top surface remove CO2 and nitrogen from the air through photosynthesis. They protect and colaborate with other species in the next layer that fix the nitrogen but cannot stand oxygen. These species have coevolved to work together to hold the soil together and support the growth of more complex vascular plants.
Almost invisible to the naked eye, this crust ecosystem stabilizes the soil while fixing carbon and nitrogen. When the delicate crust community is destroyed, plants starve for nitrogen unless they are given massive fertilizer applications. Chemical fertilizers are an environmental nightmare which release lots of nitrous oxide into the air. Nitrous oxide is 298 times worse than CO2 as a greenhouse gas. Fertilizers also pollute streams, consume fossil fuels and emit CO2 in their manufacture.
Bioinoculants can restore degraded soils by adding natural microorganisms that greatly reduce the need for chemical fertilizers and even water in the soil. Dramatic increases in soil carbon are possible in a single season. Damaged soil crusts could be healed by aerial spraying of tiny amounts of cyanobacteria mixtures which remain viable through long periods of dryness yet rehydrate and begin growing within minutes of receiving rain or even dew condensation. Cyanobacteria were responsible for creating the oxygen on our planet from CO2 billions of years ago. Perhaps they can help us to rescue the planet today.
Another promising approach to greening deserts is seawater farming. Coastal desert areas lacking fresh water can grow plants like Mangrove and Salicornia along with fish and shrimp that provide the fertilizer. The first commercial-scale saltwater farm was built by the Seawater Foundation on a barren desert in Eritrea, on the west coast of the Red Sea. Before the project, ecologists found only 13 species of wild birds in the area. By the time the farm was completed in 2002, the count had increased to 200. Here is a movie about that farm.
Another massive farm is planned for Abu Dhabi. Boing and Honeywell are partners in the project, which will grow salt-water biomass to be used for making green fuel for jet aircraft. There are 25,000 miles of coastal desert in the world that could be developed in this way. Carbon trading could be the driver for these projects if we can only develop sound verification protocols and measuring instruments.