Land Use Part II: Agricultural Issues

Pesticides – Agricultural Chemicals Industrial agriculture relies on pesticides to produce their crops. A pesticide Is a poison used to destroy pests, such as insects, rodents, or weeds Pesticides can also harm: Beneficial plants and insects, wildlife and people

Pesticide Resistance Pesticide Resistance Over time, spraying large amounts of pesticide to get rid of pests usually makes the pest problem worse. Pest populations may evolve resistance Most surviving individuals have characteristics that allowed them to tolerate the pesticide. Survivors pass on genetic characteristics for tolerance. Subsequent pesticide applications become less effective. More than 500 species of insects have developed resistance to pesticides since the 1940s.

Persistence Persistence Does not break down easily or quickly in the environment. Do not break down into harmless chemicals, and they accumulate in the water and soil. Some pesticides have been banned in the United States for decades but can still be detected in the environment. Persistent pesticides become attached to small soil particles and are easily moved by wind or water. Persistent pesticides have been discovered in polar ice and are present in detectable amounts in the bodies of animals, including humans, throughout the world.

Agricultural Chemical Use Herbicides Are used to control unwanted plants. About 60% of pesticides used in U.S. are herbicides. Weeds compete with crops for soil nutrients. Traditional weed control methods are expensive in terms of time and energy. Several major types of herbicides are in current use. Auxins Synthetic plant growth regulators mimic natural growth regulators Photosynthetic disruptors Enzyme inhibitors

Some herbicides are toxic to all plants (nonselective), and some are selective as to the plant species they affect. Atrazine is often used to control broad-leaf and grassy weeds. Glyphosate (Roundup) is a broad-spectrum, nonselective, systemic herbicide used to control plants. Fungicides are used to protect agricultural crops from spoilage, to prevent the spread of disease, and to protect seeds from rotting in the ground before they can germinate. Methylmercury is extremely toxic to humans. In some parts of the world, governments pay a bounty to people who kill rats because they can destroy agricultural crops. Rodents also carry diseases harmful to humans. Rodenticides must be used with great care to prevent poisoning nontarget organisms.

Problems with Pesticide Use Bioaccumulation is the process of accumulating higher and higher amounts of material within an organism’s body. Many persistent pesticides are fat soluble and build up in fat tissues. Biomagnification is the process of acquiring increasing levels of a substance in bodies of higher trophic-level organisms. DDT, mercury, and PCBs are all known to accumulate in ecosystems. DDT was banned in the U.S. in the early 1970s.

Problems with Pesticide Use Pesticide resistance is a problem associated with the widespread use of pesticides. Most pesticides are not species-specific, and kill beneficial species as well as pest species. Many kill predator and parasitic insects that normally control pest insects. Insecticides may change the population structure of the species present so that a species not previously a problem may become a serious pest. Pesticides are designed to kill organisms, so they may also be dangerous to humans. Short-term and long-term health effects to persons applying pesticides and the public that consumes pesticide residues in food are also concerns.

Acute poisoning during application sometimes occurs when farmers cannot read caution labels on packaging or do not have access to protective gear. The WHO estimates between 1 million and 5 million acute pesticide poisonings occur annually, resulting in 20,000 deaths. For most people, the most critical health problem is inadvertent exposure to small quantities. Farmers who were occupationally exposed to pesticides over many years show that they have higher levels of certain kinds of cancers than the general public. Chronic minute exposures to pesticide residues in food or through contaminated environments are also of concern.

Why Are Pesticides So Widely Used ? Food Production Worldwide, pests destroy 35% of crops. This represents an annual loss in U.S. of $18.2 billion. Economic Concerns Pesticides increase yields and profits. Health Reasons Insecticides curtail many diseases.

Problems with Pesticide Use A perfect pesticide would have the following characteristics: Inexpensive Only affect target organisms Short half-life Break down into harmless materials Newer pesticides have fewer drawbacks than early pesticides, but none are devoid of problems.

Rachel Carson – Silent Spring

How is Arable Land Lost? Land Degradation ha stands for hectare Which is 10,000 square meters or about 2 and a half acres. 3 million ha of cropland ruined annually via erosion 4 million ha transformed into deserts 8 million ha converted to non-agricultural uses Converting arable land with subdivisions Over the past 50 years, 1.9 billion ha of agricultural land has been degraded.

Arable Land Unevenly Distributed North America and Europe are particularly well suited to growing while some other parts of the world lack suitable soil, topography and water. The amount of available cropland is shrinking. Exceptions are South America and Oceania, where forests are being converted to farms Gains in agricultural production have come from increased fertilization, pesticides and irrigation rather than more land.

Land Degradation Definitions of degradation are based on both biological productivity and expectations of what land should be like. Generally, land is considered degraded when Soil is impoverished or eroded Run-off is contaminated Biodiversity is diminished. Water and wind are the driving forces for vast majority of soil degradation.

Erosion Erosion is a natural process, resulting in redistribution of the products of geologic weathering, and is part of both soil formation and soil loss. Worldwide, erosion reduces crop production by equivalent of 1% of world cropland per year. Erosion results in sediment loading of rivers and lakes, siltation of reservoirs, and smothering of wetlands and coral reefs. Wind can equal or exceed water as an erosive force, especially in a dry climate and on flat land.

Desertification Conversion of productive lands to desert threatens 1/3 of the earth’s surface and 1 billion people Rangelands and pastures are highly susceptible (overgrazing, soil degradation). Africa and China are of particular concern. Rapid population growth and poverty create unsustainable pressures. Removal of trees for fodder and firewood triggers climate change that spreads desertification.

Soil Degradation in the U.S.

Genetic Engineering and Agriculture Removes DNA from one organism and splices it into the chromosomes of another. Produces genetically modified organisms (GMOs) with new traits. Can produce crops with pest-resistance and wider tolerance levels to frost, drought, low nutrient soils, salty soils, etc. Can improve protein or vitamin content of crop Can incorporate oral vaccines into foods such as bananas for use in developing nations Animals can be modified to grow faster or produce pharmaceuticals in their milk. It differs from traditional breeding methods in that desirable genes from any organism can be used, not just those from the species of plant or animal being improved Can also be called transgenic organisms

Examples of GMO’s Biotechnologists have recently created plants containing genes for endogenous insecticides. A gene from the bacterium Bacillus thuringiensis (Bt) makes toxins that are lethal to butterflies and beetles. These genes have been transferred into corn, potatoes and cotton. Reduces pesticide use and increases yield. Concern has arisen over several points. Spread of genes into wild populations leading to resistance in pests Effect on nontarget species Transgenic crops can be engineered to tolerate high levels of pesticides. Roundup Ready and Liberty Link are two most popular. Crops can grow in the presence of the pesticides (called Roundup and Liberty) while weeds within the field are killed.

Issue with GMOs Concerns about GMO seed or pollen spreading in wild Produce superweeds resistant to pesticides. Native biodiversity may be reduced. Novel toxins might be created Cartagena Protocol on Biosafety regulates these concerns US is an active observer Knowing what foods have/are GMOs Determined to be safe for human consumption GMOs are not currently labeled FDA finds it would be counterproductive and expensive to label You are already eating GMOs as 60% of processed food in the U.S. contains GMOs. Technology may only be available to the rich, making family farms uncompetitive and driving poor nations further into poverty.

Environmental and consumer groups have campaigned against GMO’s European nations have bans on GMOs. Worry that genetically modified animals will escape captivity and outcompete their wild relatives. Salmon with added growth hormone gene grow 7X faster than their wild counterparts.

Domestication and Genetic Diversity Domestication of crops and livestock causes a loss of genetic diversity Farmer selects and propagates animals with desirable agricultural characteristics Many high yielding crops are genetically uniform High likelihood that bacteria, fungi, viruses, etc. will attack and destroy entire crop Increasing Livestock Yields Hormone supplements US and Canada do this Europe does not citing human health concerns

Concentrated animal feeding operations In North America animals are fattened on grain in feedlots Local air and water pollution caused by untreated waste Waste can contaminate soil and food. Recent spinach contamination High density of animals requires constant use of antibiotics, leading to antibiotic resistance in microbes. 40% of antibiotics produced in US are used in livestock operations Problems with increased bacteria resistance

This American Clip – 5:27

Seafood Aquaculture supplies food, but it uses wild populations to stock and feed captive populations destroys mangrove forests and wetlands used as nurseries for all marine species allows the spread of disease releases large quantities of feces, antibiotics and other pollutants

The Problems With Monocultures Biodiversity loss Loss of habitat through conversion of grasslands and forests along with wetland draining Fish kills from agricultural runoff Extermination of predators Loss of genetic diversity due to monocultures Genetic pollution from bioengineered or selectively bred organisms that “escape” and interbreed with native species Spread of diseases from agroecosystems to natural ecosystems Water Aquifer depletion Increased runoff, due to land clearing and plowing Sediment pollution from runoff Fish kills from pesticide runoff Surface and groundwater pollution from pesticides, antibiotics, and fertilizers Over-fertilization of lakes, rivers, and coastal ocean from fertilizers, livestock wastes, and food processing wastes