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

April 22, 2012

Can California agriculture help increase carbon sequestration?

The carbon cycle is currently out of balance. Humans have introduced too much carbon dioxide to the atmosphere from burning fossil fuels, causing climate change and changing weather patterns. We have the technology to do work with nature to sequester more carbon. Agricultural land accounts for 455 million acres of the total land area in the US of 1.9 billion acres. Unfortunately, since the time that we have settled the land, the soil organic content has dropped to about less than one-fourth of what it once was.

Humans could sequester organic carbon into soil if we operated farms and ranches with practices that increase and maintain the organic material in the soil. For example, conventional farm practices that include improper tillage and overuse of chemical fertilizers result in about 20,000 pounds of carbon dioxide. We can help control the CO2 released by adding organic material to the soil. Practices in which soil is mulched and rarely tilled result in a dramatic decrease in the loss of carbon dioxide from the soil. Tilling the soil upsets soil life and exposes it to sunlight and oxidation, releasing large amounts of CO2. In the natural environment, the carbon-based roots and other soil life are rarely exposed or destroyed. Such oxidation naturally takes place, but the natural process is much slower, so plants can capture the CO2 and reprocess it instead of letting it into the atmosphere.

California is a huge venue for carbon storage potential, as much of California’s agriculture is perennial. Perennial crop residue is more readily decomposed than annual residues, and perennials store carbon within the woody biomass of trees and vines. Further, with the increase in agricultural yields, the biomass returned to the soils has increased, promoting sequestration. Rice farmers have also contributed to sequestration efforts. Instead of burning the fields after harvest, most of the crop residue is now returned to the soil. Through similar small efforts, California agriculture can greatly increase its agricultural carbon sequestration.

Although there has not been significant research into vineyards as carbon sequestration resources, they hold high potential. Permanent cover cropping has been shown to increase soil organic matter when used instead of bare fallow rotations. Growing cover crops, however, can be negatively impacted by one light tillage annually. Further research is needed to understand the ability of different cover crops to increase soil carbon in vineyards. Still, there have not been many studies of vineyards and carbon sequestration. Vineyard specific studies are needed to understand the effects of vineyard management practices on carbon storage.

California could almost double carbon sequestration by adapting conservation tillage practices and returning prunings to the soil. This assumes that area for perennial agriculture continues to expand, and that the biomass of crops continues to grow. As of 2002, California’s agriculture was not sequestering through conservation tillage although the practice is commonly cited as sequestering carbon by reducing soil respiration. Due to the low erosion potential of the land and the high intensity multicropping, California agriculture has not widely adopted conservation tillage. If further research were done on adapting conservation tillage to California agriculture, we could help restore balance to the carbon cycle.


Christopher Miranda is an undergraduate in the USC Dana and David Dornsife College of Letters, Arts and Sciences.

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.

February 14, 2012

California Coastal Sage Habitat: On the Brink of Extinction

Many residents of Southern California are unaware of the growing threat to the California coastal sage habitat. This widespread ecosystem ranges from central to southern California. The habitat is known for its high species and soil biodiversity as it houses a wide range of organisms and diverse soil levels. This region is threatened by human and agriculture expansion and consists of diverse habitats that range from forests to woodlands to grasslands and salt marshes.  Because of this variety of habitats, the soils in these regions have to be able to support the growing habitats and ensure their survival.

The eco-region of the coastal sage habitat is home to about 200 species of butterflies, the widest range of native bees in the United States, and a wide variety of other organisms that rely on this region for their home. The California legless lizard and the rosy boa are just some of the reptiles and amphibians that belong to this certain Southern California region. The Channel Islands also take part in this eco-region, but because they are isolated, they house certain rare plant and animal species that are only native to that island.

Because of anthropogenic development, native habitats in this region are threatened. Human air pollution, specifically smog, reduces production and growth in the environment. When humans introduce outside species, such as sheep, cattle, and deer, their grazing and physical presence on the land reduces the productivity and fertility of the land. Agricultural practices do not allow for healthy regrowth of the soil and plants. Only about 15% of the coastal sage habitat is intact because of the growing expansion of agricultural lands and housing. Human invasion of this land has altered the physical makeup of the region enough to affect the organisms that live on and in the soils. Invasive plants, brought in by humans, displace native species, which change the flora and fauna of the specific eco-region.

Since humans have started to develop the land, the larger habitats are divided into smaller regions. These small habitats are more vulnerable to outside threats of animal and human predators. Humans use processes such as grazing, herbicides and burning to convert the land to their specifications. However these methods alter the soil composition, which affects the organisms that live in the soil and the organisms that rely on the soil. These unfamiliar conditions destroy the native seed beds and organisms within the soil, which negatively impacts soil productivity. Unhealthy soil leads to overall ecosystem degradation.

Because of these huge environmental impacts and risks, conservation ecology is crucial to preserve this eco-region from becoming extinct. Not only are the organisms threatened, but the diversity of the soil relies on the preservation of this coastal sage habitat. Many humans are only concerned with development and expansion, but for human society to thrive, the environment surrounding humans needs to thrive as well. With population increasing, we can’t ignore human needs, however there has to be a balance between human and environmental needs. Destroying this coastal sage habitat threatens the ecosystem services that communities depend on, such as water, oxygen from the wide range of trees, food, and other vital resources.  There needs to be a bigger focus on soil preservation and protection of organisms in this region because many of them are so rare and specific to this coastal sage region. Without this eco-region, a whole group of organisms would become extinct. We might not even know the benefits of all of these organisms, and to destroy them in order to expand our agricultural land, would be a huge loss to this treasured habitat in Southern California.


Chantal Morgan and Alanna Waldman are undergraduates in the USC Dornsife College of Letters, Arts and Sciences.

September 25, 2011

California Wildfires

Soil biodiversity and conservation ecology has become a hot issue, specifically in Southern California, due to numerous factors. Due to anthropogenic factors such as human caused wildfires, and use of fertilizers on grasslands, Southern California’s soil is losing nutrient richness, and a decline in productivity is occurring. Other naturally occurring factors that contribute to the decline in suitable soil in Southern California are sediment deposits and high winds.

In the case of California wildfires, as explained in the article Ecological Effects of Southern California Fires Could Be Devastating,” human induced wildfires are much more harmful to flora and fauna than naturally occurring fires, according to Dr. James Danoff-Burg. “There are a lot of species that have adapted to a fire-dependent ecosystem,” Danoff-Burg says. “But there will be more mortality across the board, including in fire-adapted species, because these fires are more intense than normal wildfires.” Due to these intense fires, species are not only dying, but the microbes and soil productivity is decreasing.

The second anthropogenic problem in Southern California deals with fertilization. According to the abstract of “Effects of Soil Resources on Plant Invasion and Community Structure in Californian Serpentine Grassland” by the Ecological Society of America, fertilization with chemicals such as nitrogen and phosphorus have led to an increase in biomass of native vegetation initially, however by the second season the non-native grasses began to invade, and dominate areas originally inhabited by native grasses. In this instance species richness declined with fertilization due to the increase in biomass production by non-native organisms, and changes in community structure demonstrated that the invisibility of plant communities may be influenced directly by nutrient availability.

The Los Angeles Basin is where the majority of Los Angeles County inhabitants reside, and is an area high in sediment and low in stability. Due to the high deposits in sediment the area is more susceptible to ecological impacts from urbanization and urban sprawl of the Los Angeles Basin, as well as natural hazards such as earthquakes or winds. This means that one of the most densely populated regions in the United States is living directly on top of land that is very unstable, and very susceptible to earthquakes at a high frequency and high magnitude. Another effect of the instability is water supply. According to the U.S. Geological Survey, More than 10 million people live in the Los Angeles metropolitan area, and the majority depends on water pumped from beneath the surface of the Los Angeles Basin. In the central and west coast basins a third of the water consumed by the four million residents come from ground water. More than 30 monitoring wells have been drilled in an effort to better understand just how the instability of the basin could affect the future water supply.

Lastly, winds in Southern California are particularly dangerous because of the desert. Hot, dry winds blowing from the inland are very commonly called Santa Ana winds. These winds are responsible for the high frequency of wildfires in Southern California. This ecological impact is what causes the dry desert region to be so nutrient depleted. The drastically different terrains within southern California make it hard for conservation ecology to improve the soil biodiversity.

About the authors: Liam Sharkey and Katie Graves are undergraduate students in the USC Dornsife College of Letters, Arts and Sciences.

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