Food and Food Supply

1. Define food security and food insecurity.
Food security refers to the people in an area having access each day to sufficient food with sufficient nutrients. It depends on countries having the means to produce or import enough food for its population. Also, a country must make sure that there are no harmful environmental effects that can affect its ability to produce food. Food insecurity means not being able to have either enough food or food with enough nutrients each day.

2. Distinguish between undernutrition, malnutrition, and overnutrition.
Undernutrition occurs when the food an individual eats is not enough to meet its basic energy needs. Malnutrition occurs when the food an individual eats does not contain enough proteins or key nutrients. Overnutrition occurs when the food an individual eats contains more calories or more nutrients than those that are necessary.

3. Describe the effects of diet deficiencies in Vitamin A.
A lack of Vitamin A can cause increased susceptibility to common childhood infectious diseases. Children under 6 who do not get enough Vitamin A can go blind and even die.

4. What is famine? How may it affect: societies, the environment?
Famine is a severe shortage of food in a certain area. There is mass starvation, deaths, and social disruption. Societies become chaotic and many starving people migrate to other areas and there is a frantic search for food and water. Individuals also eat their reserves of grains for future years and they will kill their breeding livestock. This will have an impact on the sustainable yield of an environment, affecting its ability to provide enough food for the population in the future.

5. What three systems provide most of the world’s food?
Wheat rice and corn provide more than half of the calories consumed by the world population.

6. Distinguish among industrialized agriculture and plantation agriculture.
Industrialized agriculture or high-input agriculture is that that uses high amounts of energy such as fossil fuels, a large amount of water, uses commercial fertilizers, pesticides and produces single crops (monocultures) and raises livestock.
Plantation agriculture is a form of industrialized agriculture used in tropical developing countries. It involves growing cash crops on large monoculture plantations that will later be sold to developing countries. Forests are cleared to make room for these plantations and biodiversity is reduced.

7. What is a green revolution? What limits could these have?
The green revolution is a process that helped increase crop yields. It involved three steps: First, monocultures would consist of selectively bred or genetically engineered key crops. Second, use of large amounts of fertilizer, pesticides and water to improve yields. Third, multiple cropping would allow an increase in the amount of crops. The green revolution limits biodiversity and could have adverse effects on the soil profile of an area, thus affecting its ability to yield crops in the future.

Measuring Biomass

Biomass refers to the total number of living organisms in a certain area. It is the amount of energy that is available for the next trophic level. It is important to measure biomass because it gives an idea of the state of the ecosystem. By knowing the amount of energy available, one can know how many species it can support.

One way to measure biomass is to obtain the dry weight of an organism (since it is a rough approximation to the amount of biomass) and multiply it by the number of those organisms in a given area. The units are grams per meter squared (or cubed if it is an aquatic ecosystem). This is a commonly used method. However, the difficulty here is knowing with accuracy the total number of individuals, particularly if one wants to measure biomass in a wide area.

The way to get the 'most accurate' biomass measurement would require counting absolutely every organism. However, there are ways to get an estimate. One method is by making a transect, which means tracing an imaginary line across the selected ecosystem, and counting the organisms that are in the quadrants following the transect. That data can then be extrapolated to the rest of the ecosystem, or several transects can be made, to get a more accurate estimate.

Quadrats are another method in which a rectangular area is selected and biomass is counted in that specific place only. Random quadrats can be selected, and as with the transect, the more measurements (quadrats) you select, the better the estimate.

There is also a remote sensing technique that surveys the earth's surface from the air or using satellites. Images generated are analyzed to determine total biomass productivity. However, this is only used with producers, and works mostly on dense woodlands.

In the future, more technological tools will be developed and improved in order to measure biomass easily. This could include better imaging to determine biomass, as well as a technological tool that will help get an accurate number of the individuals of a species in an area. The main benefit is that the measurement will be non-destructive, harming no ecosystem.

After biomass is collected at different trophic levels, a biomass pyramid can be made. Here's an example of an estuary, more specifically, Chesapeake Bay. Taking the following food chain:

phytoplankton -> clams -> blue crabs -> sandbar sharks

Firstly, the units will be measured in kg per cubic kilometer, since it is a aquatic ecosystem. We can calculate the amount of each species in the food chain, and we get the following information:

There are 31,333,333 units of phytoplankton in 2320 cubic km of water in Chesapeake Bay.
There are 9,200,000 clams in that same area.
There are 278,666 blue crabs.
There is one sandbar shark.

Then, considering the weight of each specie and the area, we can calculate biomass, which then can be shown in what is known as a biomass pyramid. Results are shown below.

Bibliography:
Rosillo Callé, Francisco. The biomass assessment handbook. Illustrated ed. Earthscan, 2007. Print.

Kimball, John W. "Food Chains." Biology Pages. N.p., 23 Apr 2010. Web. 27 Aug 2010. .

Tackenberg, Oliver. "A New Method for Non-destructive Measurement of Biomass, Growth Rates, Vertical Biomass Distribution and Dry Matter Content Based on Digital Image Analysis." Oxford Journals (2007): n. pag. Web. 27 Aug 2010. .

Chesapeake Bay

Chesapeake Bay is an estuary located in the west coast of the United States. It receives water from over 100,000 streams and rivers and empties in the Atlantic Ocean. It is home to around 350 species of fish, dozens of species of shellfish and crabs, 16 species of underwater grasses. Waterfowl, ospreys, and shorebirds also inhabit nearby areas.

All of these species interact in this ecosystem, and form a very complex food web (made up of many food chains). As explained previously, the food chain begins with a producer, which in this case is the phytoplankton, which is then eaten by a number of first consumers, which are then eaten by other predators.

The main purpose of the food chain is to see how energy is transferred from one organism to another. However, pyramids are ways to obtain more data. They represent graphically how energy, matter, and population are distributed in a system. Two of them are the pyramid of biomass and the pyramid of productivity.

The pyramid of biomass shows the amount of biomass at each trophic level, which is calculated by multiplying the mass of an organism times the amount of organisms. The dry weight of an individual is roughly the same as the energy it contains.

The pyramid of productivity shows the flow of energy over time. Since energy is lost as it moves from 1 trophic level to another, the upper levels are always smaller than the lower ones. Only 10% of the energy in one trophic level is passed on to the next one.