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 • Genetic engineering – 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