IB ESS HL 2.3.22 Hl Human Impacts on Nitrogen Cycle Topic Practice

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IB Environmental Systems and Societies

Topic 1: Foundation

Topic 2: Ecology

2.1 Individuals, populations, communities, and ecosystems

2.2 Energy and biomass in ecosystems

2.3 Biogeochemical cycles

2.3.1—Biogeochemical cycles purpose

2.3.2—Cycle components

2.3.3—Carbon stores

2.3.4—Carbon flows

2.3.5—Carbon sequestration

2.3.6—Ecosystems as carbon stores/sinks/sources

2.3.7—Fossil fuels as carbon stores

2.3.8—Agriculture as carbon store/source/sink

2.3.9—Ocean carbon exchange

2.3.10—Ocean acidification

2.3.11—Alleviating carbon cycle impacts

2.3.12 (HL)—Lithosphere carbon stores

2.3.13 (HL)—Carbonate fossilization

2.3.14 (HL)—Fossil fuel formation

2.3.15 (HL)—Methane production

2.3.16 (HL)—Methane cycle

2.3.17 (HL)—Nitrogen cycle stores

2.3.18 (HL)—Bacterial roles in nitrogen cycle

2.3.19 (HL)—Denitrification conditions

2.3.20 (HL)—Plant nitrogen fixation

2.3.21 (HL)—Nitrogen cycle flows

2.3.22 (HL)—Human impacts on nitrogen cycle

2.3.23 (HL)—Haber process

2.3.24 (HL)—Nitrogen planetary boundary

2.3.25 (HL)—Global collaboration needed

2.4 Climate and biomes

2.5 Zonation, succession and change

Topic 3: Biodiversity and conservation

Topic 6: Atmosphere and climate change

Topic 7: Natural resources

Topic 8: Human populations and urban systems

IB/ESS/HL//Question Bank/Topic 2: Ecology/2.3 Biogeochemical cycles/2.3.22 (HL)—Human impacts on nitrogen cycle

Question 1

[Maximum number: 7]

Explain how human activities can impact the nitrogen cycle.

Humans can impact the N cycle in a number of ways:
a. Burning fossil fuels releases nitrogen oxides into the atmosphere;
b. ...these oxides react with water to form nitric acid, which precipitates as acid rain;
c. Acidification / plastic/heavy metal/PAH/pesticide pollution of soils damage soil microbiota responsible for nitrogen cycling;
d. Deforestation/harvesting removes plants/animals from the environment as stores of organic nitrogen / can result in runoff/leaching of nitrogen into waterways / decreases dead organic material (which contains proteins) to be decomposed/;
e. Afforestation increases stores of organic nitrogen / increases organic material (containing nitrogen) to be decomposed;
f. Humans release nitrogenous waste entering environments through sewage effluent;
g. Inorganic fertilizers applied to crops, enter water bodies through runoff and leaching/cause eutrophication;
h. Haber(-Bosch) process fixes atmospheric nitrogen into ammonia to synthesize inorganic fertilizers;
i. Eutrophic waters develop nitrogen rich sediment that, through upwelling/positive feedback, repeats eutrophic event;
j. Overgrazing/mechanisation can cause compaction of soils damaging nitrogen-cycling microbiota;
k. Planting leguminous crops increases stores of nitrates in soils / through biological nitrogen fixation (Rhizobium living in root nodules);
I. Sustainable farming techniques / e.g.no/reduced tillage/mulching/cover crop/crop rotation enhances N retention in topsoil (reduces erosion) / increases microbial decomposition (through improved soil structure/moisture);
m. Intensive/industrial animal production systems emit nitrous oxides/ammonia to environment;

Note to examiners: Accept any other human activity along with valid and significant impact

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