HELP PLEASE!!! ESPECIALLY PART 2
2. The following questions do not require the data above. Answer with the data given in each question.
i. There is a total of approximately 12.4 billion acres of agricultural land (cropland, rangeland, irrigated land) on the major continents. Given that the average Net Primary Productivity (NPP) of agricultural land is approximately 2900 kcal m-2 y-1 calculate the annual global NPP associated with these lands (your answer should be reported in SI units, i.e. Joules) [2 marks]
ii. Assume that animals (humans and domesticated animals) have a 10% energy conversion efficiency and that we need approximately 2800 kcal d-1 to survive. How many i) Human Vegetarians and ii) Human Omnivores could the planet presently support (for simplicity assume that 50% of the energy content of the omnivore diet comes from meat or meat products). Comment on the implication of this calculation. [4 marks]
To answer part 2.i, we need to find the annual global NPP associated with agricultural land.
First, we need to convert the given average Net Primary Productivity (NPP) from kcal/m^2/year to Joules/m^2/year. We know that 1 kcal is equal to approximately 4184 Joules.
Therefore, the conversion factor is 4184 Joules/kcal.
Given that the average NPP is approximately 2900 kcal/m^2/year, we can calculate the NPP in Joules/m^2/year as follows:
NPP (J/m^2/year) = 2900 kcal/m^2/year * 4184 Joules/kcal
Now, let's calculate the NPP per year for the total agricultural land:
Total NPP (J/year) = NPP (J/m^2/year) * total agricultural land (m^2)
We are given that there is a total of approximately 12.4 billion acres of agricultural land. To convert acres to square meters, we can use the conversion factor: 1 acre = 4046.86 square meters.
Hence, the total agricultural land in square meters is:
total agricultural land (m^2) = 12.4 billion acres * 4046.86 m^2/acre
Finally, we can calculate the annual global NPP associated with these lands:
annual global NPP (J/year) = NPP (J/m^2/year) * total agricultural land (m^2)
To answer part 2.ii, we need to calculate the number of human vegetarians and human omnivores that the planet can support based on energy conversion efficiency and energy requirements.
Given that humans and domesticated animals have a 10% energy conversion efficiency, we assume that only 10% of the consumed energy is converted into usable energy.
We also know that we need approximately 2800 kcal per day to survive. To convert this to Joules, we can use the conversion factor: 1 kcal = 4184 Joules.
Hence, the energy requirement per day in Joules is:
energy requirement (J/day) = 2800 kcal/day * 4184 Joules/kcal
To calculate the number of human vegetarians the planet can support, we divide the total NPP associated with agricultural land (from part 2.i) by the energy requirement per day (Joules/day) per vegetarian:
number of human vegetarians = annual global NPP (J/year) / energy requirement (J/day) per vegetarian
To calculate the number of human omnivores, we assume that 50% of the energy content of their diet comes from meat or meat products. Hence, the energy requirement per day for an omnivore is:
energy requirement (J/day) per omnivore = energy requirement (J/day) per vegetarian * (100% + 50%)/100%
Finally, to find the number of human omnivores the planet can support, we divide the total NPP associated with agricultural land (from part 2.i) by the energy requirement per day (Joules/day) per omnivore:
number of human omnivores = annual global NPP (J/year) / energy requirement (J/day) per omnivore
The implication of this calculation is that the number of human vegetarians the planet can support is typically higher than the number of human omnivores because a vegetarian diet requires less energy and resources compared to an omnivorous diet.