|Down to earth|
|Tuesday, 08 May 2012|
Natural forests are important in mitigating climate change impact, not only because its trees and other plant life store carbon that would otherwise as carbon dioxide join the gases trapping heat in the atmosphere and warming the globe.
The soils that are part and parcel of natural forests also store carbon, and on a larger scale. Indeed, the carbon in the top meter of earth's soil at 2.2 trillion tons is three times as much as either the carbon in the air, or the carbon in the planet's trees and plants.
On the other hand, without the forest trees and plants, there would not be much of soil in the first place. In that sense, trees and other plants are mother to soil. Soil is a product of thousands of years of breaking down of rock and its colonization by plants and biota (including bacteria, fungi, protozoa, nematodes, and earthworms).
About a third of the carbon in soil is inorganic, non-biodegradable, often found in the form of minerals and important in arid and semi-arid lands having low rainfall. The other two-thirds of the soil carbon is organic, formed by the decay of leaves, branches, trunks, fruits and roots, animal wastes and remains, and crop residues into what is called soil organic matter (SOM). Through SOM, half of which is carbon, carbon is recycled from plants and animals into the soil. Thus, whatever carbon the trees and other plants draw from the atmosphere and then converted into carbohydrates is eventually brought down to earth, literally.
Carbon is special to forests and life in general because of its unique stable and bonding properties. And forests play a special role in the cycling of carbon, storing 73 per cent of the earth's carbon in the trees, but even more in the forest soil.
Soil also plays an important role in the cycling of other major nutrients such as nitrogen, essential in biosynthesizing the basic building blocks of plants and animals, including nucleotides for DNA and RNA, and amino acids for proteins.
It is largely bacteria living in and hosted by the soil - 40 million bacterial cells per gram of soil - that "fix" nitrogen in the atmosphere to convert into forms that plants can absorb through their roots. Plants grow faster and slower depending on their uptake of nitrogen from the soil with the aid of bacteria. Bacteria play a crucial and giant role in ecology that its total biomass exceeds those of plants and animals combined. Along with fungi, nematodes, and earthworms, bacteria make up the great living part of the soil that makes plants, animals, and human life possible.
There are still other nutrients, especially minerals, such as potassium, phosphorus, calcium and magnesium that are also essential to plant, animal, and human life. The great decomposers in the soil, bacteria and fungi, break down into simpler molecules the more complex organic molecules in the SOM of forest and crop residues so that plants can absorb these mineral nutrients through their roots and water.
Throughout history, people and communities have principally relied on vegetables, fruits, tubers, and grains directly for their minerals. How much minerals they take in ultimately relies on how much minerals broken down by bacteria the soil contains. Soils deficient in minerals eventually lead to mineral deficiencies among humans, and are associated with susceptibility to infections and a multitude of degenerative diseases including cancer, diabetes, heart disease, and dementia.
But soils with their bacteria not only give forth what is healthy, but also take away what is unhealthy for people. Bacteria in the soil are found to biodegrade toxic organic compounds, whether natural or man-made.
Soil with the healthy natural balance in its SOM, including humus, bacteria, fungi and earthworms, and its inorganic part, including clay and minerals, are better able to stick together. In this way, such soils are able to deliver the rich amounts and variety of minerals that people need to stay healthy.
And finally, soil plays a key role in regenerating the cycle of water. From the soil, water, along with dissolved nutrients, seeps into trees and other large plants through the roots and is pulled up by the trees' own release of 90 per cent of the water as water vapor through their natural pores. The more water is available to trees, or the more water in and under the soil, the more water that can be sucked up and emitted as water vapor and as forest green water.
As explained by the United Nations Environmental Programme (UNEP) in its 2012 Yearbook, SOM makes water better able to infiltrate soil, and forest soils better able to hold and retain water, reduce run-offs, and slow down its flow from upland to lowland. Finally, when the soil is undisturbed and moist as in conserved and truly protected natural tropical rainforests, the SOM takes much longer to decompose, allowing the organic carbon in and above the soil to build up.
Soil degradation, loss, and erosion
And yet, while soil is so essential as a life-giving common good of Planet Earth, it is undergoing a critical level of degradation and massive loss of soil carbon, nutrients, bacteria, earthworms, and moisture. Worldwide, 75 million tons of soil are eroded each year by wind and water. Much of the erosion can be traced to the still and increasingly degraded state of the world's forests, with deforestation still unabated at 13 million hectares per year across the globe.
Also singled out as patently unsustainable in the UNEP report is agricultural monoculture: "Modern industrialized crop production relies on monocultures of highly efficient cash crops, which generally create a negative carbon budget." According to UNEP, since the 19th century, the world's use of the land has resulted in the loss of 60 per cent of its carbon in its soil and vegetation.
UNEP reports that of the 1.56 billion hectares of arable land used worldwide for crop and livestock production, only 32.2 million hectares or roughly two per cent are being farmed organically. The overwhelming bulk of agriculture is inorganic and polluting, using chemical fertilizers, pesticides and herbicides, fossil fuels, and increasingly herbicide-dependent genetically modified seed varieties. As a result, soils have become acidic, degraded of their nutrients, bacteria, fungi and earthworms, and are thereby less productive and nutrition-friendly.
The grim verdict of the UNEP report is that over the past 25 years, a quarter of the globe's land area suffered a decline in its productivity and its ability to provide ecosystem services to people.
Increasing organic matter in soil
Sadly, the Philippines also chalked up a similar record in the health and quality of its soil environment. A global study estimated that roughly 13 million hectares or over 40 percent of the country's land area is degraded. According to the government's Bureau of Soils and Water Management (BSWM) of the Department of Agriculture (DA), estimates also place the volume of soil lost through erosion in the country to be one meter deep over 200,000 hectares each year. A nationwide BSWM study over the past 30 years, but now using GIS and remote sensing technologies, traced the soil degradation to intensive logging and unsustainable upland farming methods.
Many Filipino farmers have embraced the virtues and benefits of organic farming, but Agriculture Secretary Prospero Alcala admits that Philippine organic farming is still in its "formative years." The experience of organic farming, such as in globally-awarded Dumingag, Zamboanga del Sur (see ESSCNews), shows that it can generate productive yields and cut farming costs, free from expensive chemical inputs. But it also shows that organic farming and farmers need massive government macro-economic policy, marketing and investment support, at least initially, in terms of price subsidies and guaranteed markets. Eventually, this support could further drive up organic farm sales and productivity so that these subsidies may no longer be needed in the future, once food consumers enjoying rising income are better able themselves to directly support organic farmgate prices and higher farmer income.
Despite declared official policy under the Organic Agriculture Act of 2010 "to implement Philippine organic farming" in order to improve soil quality, it remains greatly under-prioritized and underfunded, allotted a mere two per cent minimum in the DA's budget and receiving only PhP 900 million from the total PhP 37 billion DA 2011 budget. In addition, DA policies remain conflicted and inconsistent, heavily promoting herbicide-dependent genetically modified organism (GMO) farming, such as Bt corn and Bt eggplant, and agrochemical-dependent "hybrid" sterile rice varieties. Without an authentic major shift in priorities, the prospects for advancing significantly or far beyond current organic rice farms' less than five per cent share of Philippine rice harvests therefore appear hazy and muddled.
Worldwide, scientists are developing ways to measure, report, and verify changes in soil carbon. On the other hand, they still have to come to a universal agreement on these methods. In addition, there is also insufficient knowledge about how local soil properties and climatic conditions affect changes in local stocks of carbon in the soil and vegetation.
In spite of this, most scientists agree on the need to stop deforestation, thickly reforest degenerated lands, and reorient agriculture toward increasing organic material in the soil. Bringing farming policy and practice truly down to earth is a step in the right direction.
For the full reports, please see UNEP Year Book 2012 and Towards a Green Economy: Pathways to Sustainable Development and Poverty Eradication.