By Dr.Mohammed Sa’id Berigari, Senior Soil Scientist, USA,
21/3/2012
Our fragile and exquisite habitat, the biosphere, is changing rapidly and irrevocably, primarily by human activities. Most of the coming stresses are linked to the lands we use, thus, finding hopeful remedies depend to a great extent on a broad and deep understanding of soils. There are eight urgent issues facing humans in the coming decades: food, water, nutrients, energy, climate change, biodiversity, recycling “waste”, and global equity. Soil scientists might address these questions: by refocused research, broadened vision, enticement of emerging new scientists, and clear reviews of past successes and future prospects. The terrestrial ecosystem, our fragile and exquisite habitat on this planet is facing profound upheavals perhaps as devastating as any in human history (Moore, 2002). These rapid changes even during our short life span are mostly the result of the way we misuse soils, biota, water, and the total environment. The questions posed and responses proposed in this article are neither complete nor fully refined.
Finding right paths through the expected bottleneck (Wilson, 2002) will be a real challenge of scale and gravity not witnessed before. The starting step is by knowing and understanding our soils. New technology may delay some stresses, but the concrete answers will come from humble goals: learning how to live wisely and productively on the land.
Exploring some urgent questions facing humans in the coming decades and how we, who study the land, might resolve those challenges.
1. Food Supply: How Can We Feed a World with Billions More without Harming Soils or the Total Environment?
It is expected that word population by year 2050 may exceed 9- billion, an increase of more than 2-billion from today (United Nations, 2008). As incomes increase in developing countries so do appetites for animal products, thus, increasing the demand for feed. These factors and others have led many to predict that global food requirements may increase more than 50% by year 2050(Glenn et al., 2008).
Soil scientists are faced with fundamental questions: Where should they plan to produce more food? Where are some places for highest potential increases? Could it be in the developing countries where the demands are greatest? Where will such increases have least impact on soils and other resources?
Soil scientists will also like to ask: How should we plan to produce more? The best option might be to intensify existing farming systems with better genotypes; advanced methods of tilling, fertilizing, and planting; and more effective control of weeds and other pests. In other areas pushing current systems harder may damage, and we may need to explore rearranging systems by asking tough questions. What is the place of “organic” farming systems and of genetically reconfigured crops? How can we utilize the inborn advantage of ruminant livestock while reducing the environmental impact of some intensive feeding practices? Should we plan for more intensive production on smaller areas or environmentally safer production on expanded areas? What are the potentials of urban farming?
It is not just a question of producing more food, but also of ensuring that we do not harm the capacity of others, primarily our descendents, to obtain their food and other services from soils. The soil scientists may step beyond measuring how present ways of producing food affect the soil to exploring new methods that increase food and protect other functions of ecosystems.
2. Fresh Water Delivery: How Can We Manage Soils Wisely with Fresh Water Limitations?
The earth is bathed in water. However, all of water on the planet is about 1.4 billion km3, only about 3% is “fresh” and most of it is locked in polar ice, glaciers, and underground reservoirs, leaving only a fraction for human use and terrestrial ecosystems (Schlesinger, 1997).
For a long time, fresh water on the earth was considered abundant and used accordingly. But now fresh water is getting scarce as the demands increase and the remaining pools are being drained or polluted. Currently some underground reservoirs are being rapidly depleted, mainly by crop irrigation, and few rivers fill dams. With population growth and climate change the water shortage are likely to get worse.
How do we manage water supply in the coming decades to meet human and ecosystem demands on a warming earth? One way to satisfy demand is to rely more on vertical fluxes of water i.e. precipitation and transpiration and less on lateral fluxes (aquifers, lakes, and reservoirs) according to Falkenmark and Rockstorm (2006). Can we increase water use efficiency by managing soil disturbance, plant population, and nutrient wastes? Can better understanding of the plant-soil systems result in cultivars with higher water use efficiency? And can we lower the polluting impact of agriculture on the total environment thus, keeping more water fresh?
Alleviating the threats of water shortage is currently an urgent global demand and climate change may further enhance shortage. Most of the circulating fresh water on this planet percolates through the soil, and soil science is therefore needed not only to understand these flows but also to investigate ways of managing dwindling reserves more efficiently.
3. Nutrients Replacements: How Can We Maintain and Enhance Soil Fertility while Removing Nutrients by Huge Harvests?
With yield increases, so do nutrient removal from soils. In the US, for instance, the harvest of major crops removes annually nearly 7.8 –Tg( trillion grams) of N( excluding N2-fixing crops such as alfalfa, soybeans, and peanuts), 2.3- Tg of P, and 6.7-Tg of K, with removals increase by roughly 1% annually( International Plant Nutrition Institute, 2010).
To maintain soil fertility of the exported nutrients through harvest they need to be replenished. One way to achieve that, an approach we heavily rely on as yield increases is to apply commercial fertilizers. Nearly 40-60% of the food produced in the US and UK is due to fertilizer use and even higher proportions in the tropics (Stewart et al., 2005). Fertilizer N accounted for the food of 48% of the 2008 world population (Erisman et al., 2008).
We cannot feed the world without synthetic fertilizers. But their supplies are limited by finite reserves of energy and ores. They are also a major input cost to the farmers, and if not used wisely they can contaminate the environment. Therefore, further efforts are required to improve their efficiency (Doberman, 2007). For cereal crops the annual uptakes from the applied fertilizers is < 60% for N, P, and K, although such estimates may not include nutrients retained in the soil (Snyder and Bruulsem, 2007)
Another way is to recycle more efficiently the nutrients in the ecosystems such as those in the manure. Globally, the N supplied by animals rivals the amount added in fertilizer, but only about 40-50% of excreted N is recovered and only about half of that is recycled to cropland (Oenema and Tamminga, 2005). Nutrients in crop residue can also be used efficiently, particularly those in legume residues, which supply biologically fixed N (Doran et al., 2007).
Nutrients, soil, water, and biological resources are limited on this planet and need stewardship. For all these sources, imported or recycled, the basic strategy is simple as a concept. That is the nutrient supply is tightly linked to plant needs, thereby affording adequate nutrition while minimizing leaks to the environment. But due to many variables of nature we have not been able yet to precisely synchronize nutrient availability with crop needs.
Nutrients stewardship can often be improved by retuning the existing practices: right placement, right timing, and right forms of fertilizers. However, some inefficiencies occur from fundamental ecological disconnects
4. Energy Needs: How Can We Manage Our Soils to Meet Increasing Energy Demands?
Plant-based biofuels have emerged to prominence, as a way to relieve climate change while seeking energy security. The main processed biofuel is ethanol, primarily from grain corn or sugarcane. In the US, for instance, more than 20% of corn yield is utilized for ethanol (Tollefson, 2008). However, grain-derived biofuel is relatively inefficient and could increase CO2 emissions from land use change (Fargione et al., 2008) or N2O release from growing the crops (Crutzen et al., 2008). Ethanol production from cellulose could yield greater energy efficiency, but its technologies are still in the infant stage.
The growing demand to supply feedstocks for biofuel emphasizes the importance of carefully balancing ecological tradeoffs. If more C is used for biofuel, that leaves less for use as food, fuel, or soil replenishment (Lal, 2009). Many other questions remain unanswered. How do biofuel plants affect water use or biodiversity? Can the emissions of greenhouse gases from these crops be reduced? What are the long-term impacts of energy crops on soil salinity (Bartel et al., 2007) and other soil properties? Can the byproducts of biofuel-energy be used to improve soil quality and productivity?
The decreasing reserves of cheap and relatively clean sources of energy will affect ecosystems globally, both by making energy more expensive and by increasing the harvest of biomass for biofuel energy use. Soil Scientists need to be alert and far-sighted to make sure that these changes do not compromise the long-term ecosystems’ health and to see that gains in one sector of the environment (e.g., climate change mitigation) do induce losses elsewhere, for instance, soil quality and biodiversity loss.
5. Climate Change Threats: How Would it Impact the Productivity and Recovery of Our Soils?
Concentrations of greenhouse gases in the atmosphere are increasing rapidly. Concentration of CO2, once about 280- µL /L, now exceeds 380-µL/L, and is increasing almost by 2-µL/L per year, mostly from fossil fuel combustion but also from land use change (Canadell et al., 2007). This abrupt increase in CO2 concentration is projected to have long –term effects on the global climate and biogeochemistry, affecting ecosystems in many ways, both directly and indirectly (Intergovernmental Panel on Climate Change, 2007). For instance, higher CO2 concentrations will enhance photosynthetic rate; changes of local climates affect adaptability of animals, plants, and their pests; and warming accelerates organic matter decomposition. And altered precipitation patterns cause droughts or floods, change in weather intensity affect soil erosion, rising sea level alters coastal ecosystems. Thawing of northern soils may induce CH4 release; and shifts in arable lands may pose new threats on newly cultivated soils as farming systems move or adapt. Briefly, projected changes will stress ecosystems worldwide.
Since many of the threats from climate change affect the land, soil scientists must be at the forefront of research on climate change. First we need to better forecast, based on a deeper understanding, how coming changes will affect ecosystem’s functions. What will happen to the massive reserves of C stored in soils, wetlands, and tundra? How will climate change alter N mineralization for corn in Iowa, USA, soil organic matter in German forests, soil sediment load in the Amazon estuary, and pest control in the Serengeti?
A second objective is to help design systems on managed lands that reduce the threats of climate change by setting apart C in the fields and forests, by curtailing emissions of CH4 and NO2 from farmlands, and by supplying feedstocks for biofuels. Soil scientists should ensure that these practices are effective in the short- term, but also that they do not jeopardize long-term performance of ecosystems.
Third, soil scientists will need preparation and readiness for change. Several impeding changes have already enough momentum that certain impact is inevitable. May be the best way of embracing change (perhaps even benefiting from it) is to bolster the resilience of ecosystems, especially those dominated by humans. This means identification and protection of the most fragile systems and envision of new ones that might succeed and flourish in decades ahead.
6. Biodiversity Conservation: How Can We in Depth Understand and Enhance the Biological Communities Within and on the Soil for More Resilient and Fruitful Ecosystems?
Life on earth occurs in a dazzling pattern, embraced by flows of energy and nutrients. These myriad biota gradually evolve, some species being lost, others emerge. However, recently rates of extinction have accelerated (Scholes and Biggs, 2005) so that now conserving biodiversity is a high priority.
Soils are the natural habitat for terrestrial biota, so preserving soils is often a first step in conserving biodiversity (Lal, 2007). Moreover, soils hold an astonishing abundance and variety of organisms, many of which remain unidentified and poorly understood (Giller, 1996). In fact, “soils are one of the great frontiers for biodiversity research” (Fitter et al., 2005).
Why is it important in preserving biodiversity? First, terrestrial biota sustain many of the vital functions carried out by ecosystems, from furnishing food to filtering water to producing pharmaceuticals (Fischer et al., 2006). The microbial and fauna communities of soils, hidden and poorly understood, silently mediate countless essential processes (Coleman et al., 2004). In fact, our weak knowledge of their services may be the best reason for preserving them; without knowing exactly what they do, we cannot be sure what we have lost when they vanish. Second, biodiversity preservation offers resilience and stability to ecosystems (Brussaad et al., 2007). Although organisms carry out overlapping functions, this redundancy may offer stability and contingencies during stress and upheavals.
If preserving biodiversity is imperative, how does it affect the research we conduct? A first target, clearly, is to use new methods (Zhang and Xu, 2008) to measure diversity on and within soil. Ideally, measurements need to be carried out at a continuum of scales, from soil aggregate to our entire planet (Loreau et al., 2001) also across time, from days to decades. Wider scales also permit us to probe questions about tradeoffs; for instance, is more intensive monoculture cropland (spares diversity) justified to spare uncultivated lands (rich diversity) elsewhere (Green et al., 2005).
A second target is to understand clearly the links between diversity and ecosystem performance and resilience. We know enough to assume that biodiversity is critical but not enough to fully explain the mechanisms and complex interactions by which these benefits are delivered (Andrén and Balendreau, 1999).
Third target, we have to understand clearly how humans threaten or enhance biodiversity on and within the soil. Which farming methods enhance diversity; and which ones destroy it? What will be the effect of proposed forestry managements on the long-term soil biota? And how will impending global changes impact the countless communities of organisms that support the ecosystem functions on which we will rely into the future (Araújo and Rahbek, 2006)?
7. Recycling Disposals: How Can We Use Soils More Effectively as Biogeochemical Reactors to Overcome Contamination and Maintain Soil Productivity?
Whatever we do and wherever we go, we produce some wastes, from family dinners and family farms. The volume of our refuse increases as our population grows and our consumption intensifies, and wise use of disposals becomes a real challenge.
Many problems of waste emerge from a linear view of industrial processes: raw materials enter at one end, and products and wastes appear at the other end. This linear process creates two problems: depletes raw materials at one end and excess refuse at the other. What is needed as a remedy is regenerative recycle (Pearson, 2007), where waste becomes input, a cycle that, mimicking nature, can continue endlessly.
Few examples may demonstrate the options. One option is to find ways of reusing byproducts of industrial processes, the excreta of food and fiber factories, and the debris of fisheries and forestry. A second challenge is to use wisely the growing amounts of animal manure (Russelle et al., 2007). A third path is to learn how to recycle our biological wastes and rerouting them to the land from which they came.
Soils, the site of decay, are essentials to any regenerative system, and soil scientists need to address several critical questions. What is the capacity of various soils to process wastes safely without harm to them or the water or air they feed into? What is the ultimate fate of toxins and biohazards that are applied to soils with organic amendments (Alexander, 1994)? Can we design systems that fit local recycling of products, even in cities, thus avoiding long- distance transport? In tackling these and other questions, soil scientists may help redesign systems of farming, forestry, urban, and industries to better convert wastes to useful resources.
Soils behave as agents of recycling, and also they benefit from such a process. Decomposition in soils can improve their physicochemical properties and foster energy and substrate rich environment to host a diversity of biota. However, in the long –term waste inputs must be balanced by the soils’ capacity to recycle those (Edmeades, 2003).
8. Global Out Look: How Can We Create a Seamless Perspective that Allows Us to Optimize Management Methods for Local Places, Wherever they May Exist?
The earth is a coherently connected entity, but wounds are inflicted on the landscape locally: on a farm, a forest, and a trickling stream. However, healing of the earth also occurs locally. The best way to manage the soils varies from place to place and from year to year. Due to many local factors: physical, social, and ecological, there are limited universal” best management practices.”
What would be the best way to overcome this dilemma- the need for a global perspective while tuning practices to local peculiarities? The solution may be found in crafting seamless scales of space from a soil aggregate to the planet. With careful designs such a continuum across scales permits insights and findings to be extrapolated upward, from the local to the global, and also downward, from the planet to the local sites. Soil scientists are well positioned to forge such a continuum because the object of their study, soil, is itself an extended skin stretching across all terrestrial landscapes. And if we allow “soil” to include sediment, then it includes the entire surface of the planet.
This new way of viewing the globe, in effect, allows shifting the boundaries of an ecosystem from a soil aggregate to the entire planet. A staring point may involve maintaining and expanding global database of soil, vegetation, and research results (Hartemink, 2008) making them accessible to every potential user, from farmers to scientists. And to follow changes in soils, we need networks of long-term sites, many ecological sites across biomes and land uses that need to be tested repeatedly to monitor how lands and their habitats change with time in decades. Although such networks are already operative but many gaps exist particularly in the developing countries.
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