Food Resources (Chap4) PDF

Module 4  Why Should You Care About Food Resources Nutritious diet is necessary for a healthy and productive life About 1 billion people do not get enough food to eat Food production has environmental harmful effects: – In many areas, soils are eroding faster than being...

Module 4  Why Should You Care About Food Resources Nutritious diet is necessary for a healthy and productive life About 1 billion people do not get enough food to eat Food production has environmental harmful effects: – In many areas, soils are eroding faster than being renewed – Biodiversity is reduced by clearing habitat for crops – Groundwater is depleted from irrigation in some areas – Agricultural runoff pollutes surface waters in many areas Example of the harmful effect of food production systems: (a) severe erosion of the earth’s vital topsoil. Example of the harmful effect of food production systems: (b) replacement of biologically diverse tropical forests with vast croplands such as this soybean plantation in Brazil.  What Do You Need to Know? Energy Flow and Chemical Cycling Two natural processes sustain earth - Energy flow - Sun is energy source - Energy cannot be recycled - Chemical cycling - Nutrients required by living organisms - Continually recycled Types of organisms in terms of energy - Producers - Consumers - Herbivores, carnivores, omnivores, decomposers Producers (a) include trees and other plants that live on land, as well as plants and algae that live in water. Consumers (b) include this giraffe, feeding on the leaves of a tree, as well as many other animal species such as lions, which feed on giraffes.  The Importance of Soil Soil: complex mixture of - Eroded rock - Mineral nutrients - Decaying organic matter - Water - Air - Billions of tiny organisms Topsoil - Supports plants (producers), a basic resource - Slowly renewable; can be rapidly depleted Over time, complex natural processes convert immature soil to mature soil  Types of Agriculture Several potential classifications - Traditional subsistence agriculture - Enough food to live on - Traditional intensive agriculture - Produces food to sell - Single crop (monoculture) or many crops (polyculture) - Industrialized agriculture This farmer is harvesting rice in Thailand (monoculture) This plot of land in Australia has a number of different crops planted in the same area.  Two examples of industrialized agriculture, (a) a farmer is harvesting wheat using an expensive machine called a combine, and (b) specialized equipment is being used to irrigate a crop Where our food comes from p88 p88 p89 p89 p89 p89 Protecting Crops from Pests Natural vs. Industrialized food production Natural systems have checks and balances - Predators, parasites, disease organisms Industrialized systems require inputs - Pesticides - Herbicides, insecticides, rodenticides - Broad-spectrum kill many pests - Narrow-spectrum are targeted This wolf spider helps to control pest populations by preying on insects such as this grasshopper. Wolf spiders do not harm humans Modern agriculture involves spraying chemical pesticides on crops using airplanes and ground-spraying equipment.  Meat, Fish and Shellfish Production Early livestock & fish production - Cattle in pastures and rangelands - Chickens in farmyards and fields - Fish caught in ocean, rivers or lakes Industrialized systems often different - Feedlot pack animals densely - Fed grains like corn - Large boats drag huge nets - Aquaculture (fish farming)  Crossbreeding and Genetic Engineering Early efforts at crop improvement - Crossbreeding, or artificial selection - Many current crops produced this way - Requires long periods of time Genetic engineering - Adding, removing or changing DNA directly - produces genetically modified organisms (GMOs) - Similar to crossbreeding, but can use new genes - Much faster than crossbreeding - Can yield vast improvements quickly, but controversial  Both of these tomato plants were exposed to the same destructive caterpillars. The plant on the right was genetically altered to resist pest damage. The unaltered plant (left) suffered much more damage.  Organic Agriculture - Organic agriculture - Uses mostly non-synthetic fertilizers - Mostly natural pest-control - Bans many pesticides - No genetically engineered seeds - No synthetic growth hormones - No antibiotics Less than 1% of the world’s and 0.6% of U.S cropland is certified organic The production of organic fruits and vegetables is increasing rapidly.  What Are the Problems? Hunger, Malnutrition, and Overnutrition Food security often a problem - Undernutrition (hunger) common - Malnutrition (missing key nutrients) also common - Main cause is poverty - Wars, land degradation and drought Overnutrition also problem with abundant food - In U.S. 2/3 people overweight, 1/3 obese - Increases heart disease, stroke and diabetes deaths These starving children were looking for ants to eat. They were victims of famine caused by a civil war in Sudan, North Africa, between 1983 and 2005  Topsoil Erosion & Soil Degradation Soil erosion a serious problem - Loss of topsoil lowers food production - Eroding faster than produced in 38% of world - Took thousands of years to form Soil degradation also a problem - Occurs when topsoil loses ability to grow plants - Desertification common - Soil salinization (salting) of soil Flowing water from rainfall is the leading cause of topsoil erosion. Wind is blowing topsoil off the fields This map summarizes the extent of soil erosion around the world.  Desert sand dunes are moving in on cropland. This severe desertification resulted from a combination of drought and human activities, such as farming and the grazing of livestock, which destroyed much of the natural vegetation  This soil on a farm once supported crops that were heavily irrigated. Because of high evaporation rates in this arid region, irrigation water quickly evaporates, leaving behind a crust of salts where the crops once grew.  Overpumping of Groundwater Aquifers: bodies of underground water - Often used to irrigate crops - In U.S., being used 4x faster than recharge - Lack of groundwater also affects environment - Streams, wetlands dry up Harmful Effects of Pesticides Pesticides provide many benefits - Primarily increased crop yields Can be environmentally harmful - Pesticides can become pollutants - Can affect non-target species - Can kill natural enemies of pests - Biomagnification - Pests can develop genetic resistance over time - Affects on people - Poison 3 million worldwide - Poison 300,000 in U.S.  Water and Air Pollution Sediment from soil erosion widespread source of water pollution - Smothers aquatic plants, fish, and shellfish - Disrupts life in rivers, lakes, and coastal systems Nitrate and phosphate also problems - Explosive growth of algae - Later decomposition absorb oxygen from water - Creates anoxic (dead) zones Air pollution from machinery emissions This lake has received excessive amounts of plant nutrients such as nitrogen and phosphorus from the surrounding land, much of it applied as fertilizer for crops. As a result, the lake’s surface is covered with mats of algae and other aquatic organisms  Potential Hazards of Genetic Engineering Genetic engineering can increase food security - Increased food production Some potential hazards - Mixing genes from different species - Possible unintended and unpredictable results - Pollen from GE spreads to non-GE corn  Loss of Biodiversity Loss of biodiversity - May be major threat to life - Loss of diverse forest and grassland for grazing - Loss of agrobiodiversity - Loss vegetables, fruits, and grains - Just a few varieties used - Earlier in India 30,000 varieties of rice - Current 10 varieties produce 75% of rice  Impacts of Industrial Meat & Fish Production Increased affluence = increased meat production - Degradation of land by overgrazing - Feedlots produce lots of animal wastes - Long transport distances - High use of chemicals and fertilizers Industrial fish production - Destruction of habitat, particularly coastal - Nutrient and disease problems - Reduces fish biodiversity This whole area was once typical of rangeland used for grazing. Now, the land to the left of the fence has been overgrazed, while the land to the right of the fence has been lightly grazed by livestock. Raising large numbers of fish in offshore underwater cages can pollute coastal waters with fish wastes and with the antibiotics used in their feed to promote rapid growth.  What Can Be Done? Producing More Food Commonly more food = more land used; however: - Potentially double cropland area - Clear tropical forests - Cultivate marginal land (e.g. steep slopes) - Irrigate more land - So: enormous negative environmental effects We could shift to modified food production systems with less impact and increase efforts to slow population growth  Reducing Soil Erosion Key is increased soil conservation - Systems to reduce soil erosion - Terracing - Contour planting and strip cropping - Alley cropping agroforestry reduce wind - Reduce tillage  Farmers can reduce topsoil erosion by planting along the contours of the land (contour planting) and on alternating strips of land (strip cropping). One way to reduce topsoil erosion is to grow crops in rows, or alleys, between rows of trees. Here, wheat is planted between lines of fast-growing trees in the state of Punjab, India. Farmers protect topsoil from wind erosion by planting strips of trees that serve as windbreaks along the edges of their crop fields.  Restoring Soil Fertility & Reducing Degradation Best way soil conservation - Restoration of soils sometimes needed - Add nutrients - Synthetic - Organic - Crop rotation - Plants that add nutrients - Preventative approaches: reducing overgrazing, not clearing vegetation This pile of decayed organic matter, or compost, can be used as a soil conditioner to help restore nutrients to topsoil.  Fighting Crop Pests Synthetic pesticides have advantages and disadvantages Ecological and biological control often possible - Integrated pest management (IPM) - Requires long-term approach - Importation of predators - Requires knowledge of ecosystems  This ladybug beetle is preying on an aphid, a highly destructive insect pest. Ladybugs also eat plant mites and scale insects.  Polyculture Polyculture - Possibly more sustainable - Grow as many as 20 different crops together - Can reduce chances of losing most of crop - Better resistance to extremes - Can use water and nutrients more efficiently - Weeds can be les a problem - More cover = less soil erosion Polyculture, such as that being practiced on this plot of land, has many benefits.  Making the Transition to More Sustainable Food Production Organic farming has advantages - Improves soil fertility, reduces erosion - Eliminates much of water pollution - Sharply reduces air pollution and GHG - Benefits biodiversity - Uses third less energy Disadvantages - Lowers yields by 20% - More labor