Chapter 11: Agriculture, Aquaculture and the Environment

Overview An Ecological Perspective on Agriculture Can We Feed The World? What We Grow on the Land Soils Controlling Pests The Future of Agriculture Genetically Modified Food: Biotechnology, Farming, and Environment Aquaculture

Agroecosystem Ecological succession stopped to keep the agroecosystem in an early-successional state Focus on Monoculture Monoculture - large areas planted with a single species Counteracted by crop rotation Crops planted in neat rows and fields Makes crops vulnerable to pests

Agroecosystem Farming greatly simplifies biological diversity and food chains Plowing is unlike any natural soil disturbance Nothing in nature repeatedly and regularly turns over the soil to a specific depth Genetic modification of crops

Can We Feed the World? To answer this we must understand how crops grow and how productive they can be Most viable of human activities but is it sustainable? Regions farmed for thousands of years Farming changed local ecosystems

Can We Feed the World? History of agriculture is a series of human attempts to overcome environmental limitations and problems. Each solution creates new problems Should expect some side effects Multiple pressures on agricultural land

Can We Feed the World? As population grows, the production of agriculture must grow Food supply is already inadequate for some peoples Increasingly marginal land will need to be put into production Food supply also greatly influenced by social disruptions and social attitudes

How We Starve People “starve” in two ways Undernourishment Lack of sufficient calories in available food Manifests as famine Malnourishment Lack of specific chemical components of food, such as protein, vitamins, or other essential chemical elements

How We Starve Undernourishment Marasmus – progressive emaciation caused by lack of protein and calories Kwashiorkor – a lack of sufficient protein in the diet Chronic hunger – enough food to stay alive but can not live satisfactory or productive lives

How We Starve World food production must provide adequate nutritional quality and quantity. Food emergencies affected 34 countries worldwide at the end of 20th century Africa has the most acute food shortages Food distribution major problem World food aid does not meet all the caloric need of people Best solution is to increase local production

What We Grow on the Land Crops Of Earth’s ½ million plant species, only about 3,000 are agricultural crops 150 species cultivated on large scale Most of world’s food provided by 14 crop species 6 provide 80% of the total calories

Livestock Forage- crops grown for domestic animals In US 14 million areas of alfalfa Domestic animals include 14 billion chickens 1.3 million cattle ~1 billion each sheep, ducks and pigs 700 million goats 160 million water buffalo 18 million camels

Livestock Rangeland Pasture Large world market in small grain crops Provides food for grazing and browsing animals w/o plowing and planting Pasture Plowed, planted and harvested to provide forage Large world market in small grain crops See next slide

Livestock- effect on environment About half the earth’s land area is used as rangeland Most is easily damaged by grazing (drought) Much of the rangeland is overgrazed Grazing cattle trample stream banks and release waste into streams

Soils Soils are not just “dirt” Key to life on land Earth modified over time by physical, chemical and biological processes into a series of layers called horizons O horizon - organic layer on top of soil A (& E in some soils) horizon- upper horizon B horizon - zone of accumulation C horizon - most similar to parent material

Soils Soil fertility Soil Drainage Capacity of a soil to supply nutrients necessary for plant growth Geologically younger soils are typically more fertile Soil Drainage Soils with high clay content hold water well Soil with high sand content drain very well

Restoring Our Soils Soil erosion has decreased 40% in US Due to better farming practices Use of chemical (artificial) fertilizers increased soil fertility in 20th century Use of phosphorus (mined and in guano) in fertilizers increased soil fertility

Limiting Factors Crops require 20 chemical elements at the right amount at the right time of year Macronutrients micronutrients High-quality agricultural soil has All the chemical elements required for plants A physical structure that lets air and water move freely Retains water well Mixture of soil particle size

Limiting Factors Liebig’s Law Single factor determines the growth and therefore the presence of a species Growth of a plant is affected by one limiting factor at a time

Limiting Factors Two elements may have a synergistic effect A change in the availability of one resource affects the response of an organism to some other resource. Chemical elements may become toxic when levels are to high

Controlling Pests Pests are undesirable Agricultural pests include: Competitors, parasites, and predators Agricultural pests include: Insects Nematodes Bacterial and viral diseases Weeds Vertebrates Loss can be large Estimated at 1/3 of potential harvest and 1/10 of the harvested crop

Controlling Pests Farms are maintained in early stage of ecological succession and enriched by fertilizers and water Great area for crops Great area for early-successional plants (weeds) Weeds compete for all resources Light, water,nutrients, and space to grow

Pesticides- History Stage 1 Broad Spectrum Inorganic Toxins Search for chemicals that would reduce abundance of pests Goal was narrow-spectrum (species-specific), but most were broad-spectrum Ex: Arsenic, toxic to all life Killed pest and beneficial organisms

Pesticides- History Stage 2: Petroleum based sprays and natural plant chemicals 1930’s Ex: nicotine

Pesticides- History Stage 3: Artificial Organic Compounds DDT, broad-spectrum Aldrin and dieldrin used to control termites Problems Toxic to humans, has been found in breast milk Secondary Outbreaks Pests develop resistance

Pesticides- History Stage 4: Return to biological and ecological knowledge IPM - Integrated Pest Management Goal is to reduce use of artificial pesticides Biological control- the use of biological predators and parasites to control pests Bacillus thuringiensis (BT) - Proved safe and effective

Integrated Pest Management IPM uses a combination of methods Biological control Chemical pesticides Methods of planting crops (mixed fields) Goal can be control not elimination of pest Economically makes sense Does less damage to ecosystem, soil, water and air

Biological Control Other biological control agents Small wasps that parasitize caterpillars Both effective and narrow spectrum Ladybugs Sex pheromones (chemicals released to attract opposite sex) used as bait in traps

The Future of Agriculture Three major technological approaches to agriculture Modern mechanized agriculture Resource-based agriculture Organic food production Bioengineering

How can crop production keep up with population growth? Increased production per acre Technology driven New Crops and Hybrids New or yet unused plants could do well in poorer agricultural soil Green Revolution

The Green Revolution Name attached to the post WWII programs that have led to the development of new strain of crops w/ higher yield better resistance to disease or better ability to grow under poor conditions

How can crop production keep up with population growth? Better irrigation techniques Could improve crop yield and reduce overall water use Drip irrigation Hydroponics Eating Lower on Food Chain Same area of land could produce 10–100 times more vegetation than meat per year

How can crop production keep up with population growth? Organic faming Three qualities More like nature ecosystem than monoculture Minimizes negative environmental impacts The food that results does not contain artificial compounds One of the fastest growing sectors in US agriculture

Genetically Modified Food Scientist have been able to transfer specific genetic characteristics from one individual to another, from one population to another, and from one species to another. Genetic engineering in agriculture involves several practices Faster and more efficient ways to develop hybrids Introduction of the terminator gene Transfer of genetic properties from widely divergent kinds of life

Genetically Modified Food Considerable interest in developing crops With entirely new characteristics E.g. nitrogen fixation With tolerance of drought, cold, heat and toxic chemical elements.

Genetically Modified Crops Three methods 1. Faster and more efficient development of new hybrids 2. Introduction of the “terminator gene” 3. Transfer of genetic properties from widely divergent kinds of life

New Hybrids From an environmental perspective, genetic engineering to develop hybrids w/in a species is likely to be a benign as the development of agricultural hybrids has been w/ conventional methods. Concern that genetic modification may produce “superhybrids” Could become pest or transfer genes to closely related weeds

The Terminator Gene Makes seeds from a crop sterile Critics note Done for environmental and economic reasons Prevents a gmo from spreading Protects the market for the corporation that developed it Critics note Farmer’s in poor nations must be able to grow next years crops from their own seeds

Transfer of Genes Genes transfer from one major life form to another Most likely to have negative and undesirable impacts E.g., Bacillus thuringiensis Produce toxin that kills caterpillars Gene identified and transferred to corn Engineered corn now produces its own pesticide

BT corn contains its own pesticide in every cell of the plant. Bacillus thuringiensis bacteria (a natural pecticide). The gene that caused the pecticide (BT) was placed in corn through genetic engineering. Pollen from the BT corn is also toxic and when it lands on milkweed, monarch butterflies that eat the milkweed may die.

Transfer of Genes Bt plants thought to be a constructive step in pest control No longer need to spray pesticide Bt plants produce toxin in all cells Even in pollen that can spread Monarch butterflies that eat pollen may die

Transfer of Genes Much concern worldwide about the political, social and environmental effects of genetic modification of crops.

Aquaculture Most marine and freshwater food obtained by hunting Not sustainable Aquaculture- the farming of food in aquatic habitats Important protein source

Aquaculture Extremely productive on a per-area basis Flowing water brings food into the pond from outside Can exploit multiple niches in the pond May be able to utilize waste products (treated sewage) Mariculture - the farming of ocean fish. Also increasing production of oysters and mussels