USC Dana and David Dornsife College of Letters, Arts & Sciences > Blog

February 27, 2012

Soil Restoration via Increases in Biodiversity: Do Greater Amounts of Fungi Lead to Healthier Soil?

Filed under: Nitrogen Cycle,Soil Sustainability — dginsbur @ 10:36 am

In the dark world below the top soil, there are millions of livings that play crucial roles in the ecosystem, which human beings know little about. The soil microbe communities include fungi, bacteria, protozoa, nematodes and arthropods. Although tiny individually, their existence sustain the health of the soil and sometimes even the air above.

Many studies have shown that microbes are the key to the decomposition process, and such the nutrient cycling and nitrogen fixation of the soil. Protozoa, for example, is a single-celled animal that mainly feed on bacteria and release nitrogen and nutrient that benefit plants, whose roots protozoa normally concentrate around. Protozoa would be consumed by nematodes which can decay organic matters. This food web in the soil cannot even be detected by naked eyes but the lack of it could result in the degraded soil.

With increasing population, the loss of agriculture land due to the soil degradation would be a disaster to human beings. Some soil bacteria have surprising significance in the overall ecosystem. Evidence shows that some “rain making” bacteria would be brought to the atmosphere by wind and function as ice former in the air, which would result in cloud and precipitation under proper conditions.

Many studies have attempted to restore soil biodiversity in order to soil quality and ecosystem functioning. For example, a study administered in Colorado linked soil degradation, which leads to biodiversity loss, to an increase in the presence of pathogens and pests that are detrimental to the health of humans, plants, and animals. This can lead to a decrease in soil and plant productivity. Therefore, it is essential to maintain soil biotic communities in order to “assure long-term soil sustainability”. Another experiment conducted in New Mexico in 2005 was extremely successful in restoring 1.8 million acres of degraded landscape. This was due to an increase in vegetation variety and the healthy functioning of watersheds.

However, soil degradation is not only a problem in the United States but in many other parts of the world as well. For example, due to the fact that “physical disturbance is one of the principal causes of biodiversity loss in all world ecosystems”, farmers in Southern Brazil stressed minimum disturbance and thereby produced better environments for soil macrofauna, thus becoming more sustainable. The outcome of this study proved that the diversity of soil macrofauna such as termites, ants, snails, millipedes, and centipedes among many others, play a crucial role in the successful functioning of no-tillage systems

As evident, the maintenance of soil biodiveristy is an integral part of restoration ecology and the improvement of soil quality because due to its significant role in soil function and the potential risk of losing creatures that have stunning values unknown to mankind. The need for healthy soil will only become more significant in the near future as food production will have to increase to meet the demands of a growing population.


Jay Bhayani and Hongxi Zhao are undergraduates in the USC Dornsife College of Letters, Arts, and Sciences.

Which Came First: Soil Conservation or Sustainable Agriculture?

Agriculture requires fertile soils and is therefore dependent on a high level of soil biodiversity. However, agriculture itself has a major influence on biodiversity. For sustainable farming, a farmer should manage his soil’s health, ensuring that the soil will support crops for years to come. The FoodandAgricultureOrganization has historically encouraged scientists and farmers to share research and experiences for the benefit of agricultural development programs and farmers. As soil is fundamental to agriculture, it is also fundamental to human health and food security. It is important that we conserve soil biodiversity and the manage soil for the value of its ecosystem services.

One common agricultural practice, the use of fertilizer, is advantageous to the soil biota. For example, mineral fertilizers can increase the abundance of nematodes. However, because soil biodiversity is very sensitive to the changes in soil pH and the concentration pore water salts, using fertilizer might decrease the soil biodiversity. It is important to use the appropriate amount of fertilizer to avoid damage to the soil organisms.

Pesticides are also commonly used, and can affect soil biota. Soil organisms can be exposed to applied pesticides, so it’s important that the pesticides don’t harm the soil organisms. Testing has led to the development of regulations to ensure that when used properly, pesticides will not cause unacceptable harm to the soil organisms. When planning for fertilizer and pesticide use, a farmer can work towards improving soil biodiversity. By using an appropriate amount of fertilizer and pesticides, the farmer can stimulate plant and soil organism growth while decreasing the risk towards soil organisms.

The farmer can use several physical techniques to manage his soil. The first is planting his crops. By providing plant cover for the soil, the farmer protects his soil and the organisms with in his soil from wind or water erosion. Further, cultivation of row crops such as sugar beet, maize, potato and vegetables provides only partial soil coverage and protection, leaving the land vulnerable to erosion. Large field areas are often devoid of any morphological structures, such as hedges, that could potentially mitigate erosion from wind or water. The farmer might also reduce or even stop tilling the fields. Intense mechanical soil treatment that disturbs the soil pore system is a common cause of erosion. Reduction may improve soil structure, increasing water capacity, and decreasing erosion. The consequence of the erosion is usually the loss of humus and nutrients from the upper soil, leading to reduced fertility.

As such, agricultural practices and following natural processes can have tremendous influences on soil and soil biodiversity. To maintain adequate food supply, and reach sustainable agriculture, conservation of soil is the most important factor in today’s agriculture business. Farmers can conserve soil biodiversity by using contemporary agricultural techniques that cause fewer disturbances to the soil than traditional techniques. Although soil analysis may be an extra cost to production, the benefits would outweigh the cost. With analysis and proper planning, the farmer will be able to enjoy his soil for a lifetime. Through effective soil management, the farmer can avoid stripping the land of nutrients.

As the world’s population grows and its food needs increase, we must work to relieve population pressure on food supply. Soil biodiversity is the key factor for sustainable agriculture, and thus the practices to conserve soil biodiversity are important. As the soil biodiversity and agriculture are the basis of human food supply, we need to take action to preserve our soils.


Wonho Jung and Christopher Miranda are undergraduates in the USC Dornsife College of Letters, Arts and Sciences.

California Desertification: Too Dry or Not Too Dry

Desertification is defined as the deterioration of land in typically arid areas due to changes in climate and human activities. In the United States, desertification is typically caused by poor farming practices and the conversion of grazing areas to cropland. Climate change intensifies desertification in arid areas because not only are global temperatures rising and natural disasters becoming more extreme, but also the global water cycle and precipitation patterns are such that rainfall is decreasing in most areas and concentrating in a few others. Furthermore, because California is in a climactic region that can be defined as dry subtropical, the effects of climate change and agriculture has led to increased desertification. The short-term and long-term effects of this desertification are numerous and will have many repercussions for both humans and the environment.

The environmental costs of desertification are quite serious and can eventually destroy natural ecosystems. Topsoils lose their fertility and the growth and support of organic life in the pedosphere becomes much more difficult. As topsoil drys out it becomes susceptible to movement from winds, creating new natural disasters such as the Dust Bowl of the 1930’s. Furthermore, this dust can be blown out into the ocean and can affect weather patterns. In order to salvage lands affected by desertification, farmers begin to invest more in irrigation, which in turn diminishes groundwater resources and is the beginning of long-term impacts such as drought and famine. Additionally, as the topsoil becomes less nutrient rich from desertification plants become less productive and many of the ecosystem services they were providing are diminished.

Unfortunately, California becomes more susceptible to desertification there is a tendency to focus only on the immediate effects. Important long-term impacts on the environment also need to be addressed, such as the effects on the carbon cycle, biodiversity, and freshwater supply. Vegetation in arid areas stores a substantial amount of carbon (about 30 tons per hectare) and when desertification causes drought and the vegetation dies, that storage is lost. In addition, desertification dries out soil, the organic matter of which is the largest known carbon sink, resulting in increased greenhouse gas effects as that carbon is released into the atmosphere.  As soils and vegetation are affected by desertification, ecosystems lose key resources that result in a loss of biodiversity. Desertification also poses a threat to freshwater resources. River flow rates decrease, leading to silt build up in estuaries, which incites saltwater intrusion into the water tables. As the demand for water increases there is a tendency to over-pump aquifers, which can result in water depletion and land compaction. For example, the San Joaquin Valley of California experienced subsidence at a maximum of 28 feet between 1925-1970 from overdrawn aquifers. Because California relies so much on agriculture, farmers exploit aquifer water for irrigation without considering these long-term issues. However, if the agricultural industry were to collapse from drought, we’d be facing the threat of famine and a huge economy crash.

Clearly there are many negative effects from the process of desertification that need to be addressed. Some of the most popular decisions to combat the effects of the land drying out include sustainable farming practices, such as drip irrigation, integrated crops, or no-till farming, and drought prevention. As stated in the 2010 California Drought Contingency Plan, “California’s water resources have been stressed by periodic drought cycles and unprecedented restrictions in water diversions from the Sacramento-San Joaquin Delta in recent years. Climate change is expected to increase extreme weather. It is not known if the current drought will abate soon or if it will persist for many years. However, it is certain that this is not the last drought that California will face.” The DCP has moved towards enhancing monitoring and early warning capabilities, assessing water shortage impacts, and creating preparedness, response, and recovery programs, which should help California to conserve water and slow down the desertification process.


Harriet Arnold and Divya Rao are undergraduates in the USC Dornsife College of Letters, Arts and Sciences.

The Externalities of Desalination

A few centuries ago, water use was not a problem because it was seen as a renewable resource that can never be overexploited. However, as population growth increases exponentially, water use likewise increases, depleting water resources at an unsustainable rate. As we use groundwater and surface water at a rate faster than their replenishment rate, we must look towards other sources to obtain water. One proposed solution is desalination, a process that removes salt from saline water. There are three techniques associated with desalination: electrodialysis, freezing, and reverse osmosis. Electrodialysis uses porous members to remove positively and negatively charged salt ions; freezing, by default, removes salt from ice; and reverse osmosis is a process that pressurizes salt water so that water flows through a membrane while the remaining salt are retained (Desalination Process).

Desalinization, while is considered an alternative water supply, has its fair share of negative environmental impacts that could potentially harm large communities of marine organisms.  First, the discharge from the desalination facilities carries saline water back into the ocean, which affects benthic organisms that are not accustomed to water with such high salinity. Similarly, discharged water can contain chloride, heavy metals, and cleaning chemicals that would foul ocean water and poison marine animals.

Furthermore, the power consumption required for the process of desalination consumes fossil fuels, which leads to carbon dioxide emissions. As known, carbon dioxide has detrimental effects on the environment, including warming of the earth and human health risks.

Desalination also requires an extensive amount of energy to work. If desalination were to produce half of America’s water, the United States would need to construct 100 more electric power plants (Why Desalination Doesn’t Work). And the energy cost of consuming the necessary amount of energy to produce usable water would exceed the cost to pump water from aquifers or to import the water. Therefore, desalination is not a very cost-effective method and should be used with caution.

In one example, Huntington Beach has proposed desalination in order to provide water to their community. This desalination facility, if successful, would provide 50 million gallons of drinking water per day (Proposed Desalination Plant Wins Permit). However, opponents criticize desalination as energy-intensive and expensive.  Furthermore, the construction of the facility near a popular beach would inevitably harm aquatic organisms, which could reduce tourism and recreation.

While it’s necessary to address the current water crisis and some may claim that the damage to marine organisms is insignificant in comparison to the benefits to society, desalination conflicts with the energy-crisis, which would mean that through desalination, we are essentially trading one problem in for another. Especially since most desalination plants require the use of fossil fuels, desalination would exacerbate the energy-crisis, depleting energy resources from other uses.

Despite their criticism, opponents do acknowledge the current water problem, so they propose alternative solutions, including improving irrigation systems and requiring new homes to be water-efficient.  These solutions are more focused on conservation of water, which can help communities be more conscientious of their water usage and supply more water to each individual.

Kaylee Yang and Marc Chua are undergraduates in the USC Dornsife College of Letters, Arts and Sciences.

February 14, 2012

California’s Future: Much Ado About Water

Climate change may leave California, as we know it, facing drastic reforms. As a result of heat-trapping emissions, not only will the state’s average temperature rise, but precipitation is also more likely to fall as rain rather than snow, and the snow that does fall in the Sierra Nevada’s is likely to melt earlier and more quickly. This will directly impact California residents because the snowpack formed during fall and winter provides the state with a third of its surface water, essential in the Golden State for human consumption and agriculture.  The snowpack forms in the Sierra Nevada Mountains in the upper regions of the state, but all Californians depend on it as a water source come spring and summer when the demand is at its peak. Although the California drought was declared over in 2011, the relatively dry 2011-2012 winter season has done little to restore confidence in California’s water security.

A severe reduction in snowpack, nature’s generous water storage, could likely result in inevitable major developmental changes across California. Among the most important, California’s current water reservoirs are not equipped to capture or handle larger influxes of rainwater in shorter periods of time. However, the current proposals for the expansion or addition of surface storage facilities would be minimal compared to the already existing capacity, and additional water storage facilities may be both economically and environmentally unsound. Consequently, new technologies such as large-scale rainwater capture or water-recycling plants may eventually need to be developed and implemented to ensure Californians have enough water. Additionally, California may become more reliant on alternate sources of water, increasing costs of transportation.

A water crisis could mean serious economic consequences for California. According to Frank Mittlebach, professor of Economics at UCLA Anderson School of Management, winter tourism in California, “contributed over $3.2 billion in spending in 2000.” Tourism in the mountain resort regions such as Mammoth Mountain, which is dependent on snow to attract visitors for recreational activities, has already decreased markedly this year.

More importantly, however, major water shortages would devastate California’s thriving agricultural industry, the largest in the nation, “which generated $39 billion in revenue in 2007, and which is responsible for more than half of all domestic fruits and vegetables.” One out of six jobs in California is linked to agriculture, and the state is one of the largest producers of milk, grapes, and cotton. According to UC San Diego’s Climate Research Division, the California agriculture industry could lose as much as 25% of the water it needs. Not only would this affect California residents regarding food availability and jobs, but also other states and countries due to California’s large number of exports of agricultural goods.

Overall, water as a commodity will dramatically increase in price due to higher demand and less supply.  For a state already in debt, this could lead to devastating consequences unless major preventative changes are made. If California is unable to equip its water infrastructure for the climate changes to come, stricter conservation efforts will need to be put into effect–even if it means the Southern Californians have to sacrifice their evergreen lawns.

Additional Sources:,8599,2103327,00.html

Sydney MacEwen and Danielle Tellez are undergraduates in the USC Dornsife College of Letters, Arts and Sciences.

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