chapter 14

Question 1

biomass of all mammals on earth

Answer 1

huuuge lifestock then like a fourth humans and very little wild animals that exist

Question 2

global population growth is…

Answer 2

decreasing

Question 3

Feeding the planet: issues with agriculture

Answer 3

Monocultures
Soil erosion and degradation
Water use
Artificial fertilizers
Pesticides

Question 4

Agriculture: monocultures

Answer 4

Most human food is farmed
Agriculture largely consist of monocultures
Monocultures are vulnerable to parasites and diseases

Question 5

Agriculture: soil degradation

Answer 5

Farming may lead to widespread soil erosion and degradation

Question 6

how to stop soil errosion

Answer 6

• build terraces to create level ground and stop soil washing away
• trees with roots to hold soil
• ditches conserve water
• cover crops like beans stop erosion and help absorb soil water
• mulch stops splash erosion keeps soil moist and adds organic matter to the soil
• grass bands keep teracess strong
• trash lines put weeds along contours soil buildts up behind to form a small terrace

Question 7

Agriculture: water use

Answer 7

Humans use more than half of the worlds accessible fresh water supply
Agriculture is the largest consumer of fresh water
Effects of dams:
disturb water flow to the sea
increase pollution
Lead to habitat fragmentation
Interfere with natural sedimentation

Question 8

Artificial fertilizers

Answer 8

Part of the animal waste is returned to the land
Artificial fertillizer must make up for the “gap” between plant removal and animal waste

Question 9

Nitrate pollution

Answer 9

• Nitrate (NO3-)
• Carcinogenic
• Is not retained in the soil, but easily washes out to streams and rivers
• Drinking water problem
• In natural ecosystems, most nitrate is retained in the system
• Nitrate leaks more easily from cultivated land than from natural vegetation
• Why?
• Part of the year there is no vegetation
• So if nitrate is mineralised, there are no plants to take it up
• Crops are monocultures
• No diversity in root systems or depths
• Part of the nitrate is not used
• Burning of straw and forest waste
• Organic nitrogen is rapidly transformed into nitrate
• Nitrogen in fertilizer is applied few times per year in large quantities (instead of a continuous, low production)
• The vegetation can not absorp these peak quantities at once

Question 10

Green fertilizers

Answer 10

“Green fertilizer”: use N-fixating plants to enrich the soil with nitrogen

Question 11

Cultural eutrophication

Answer 11

: excess input of inorganic nutrients from agricultural runoff and human sewage

Question 12

Dead zones

Answer 12

Anoxic parts of the ocean floor
UN report 2006: >200 dead zones world wide

Question 13

Cultural eutrophication

Solutions:

Answer 13

• Cut down the use of agricultural fertilizer
• Adapted farming practises
• Emission reduction
• Sewage treatment
• Wetland restoration

Question 14

Agriculture: Pesticides

Answer 14

Pesticides: any substance or mixture of substances intended for preventing, destroying, repelling, or lessening the damage of any pest

Question 14

Fungicides

Answer 14

for fungi

Question 15

bactericides

Answer 15

for bacteria

Question 16

insecticides

Answer 16

for insects

Question 17

Biomagnification

Answer 17

The increasing concentration of a compound in the tissues of organisms as the compound passes along a food chain, resulting from the accumulation of the compound at each trophic level prior to its consumption by organisms at the next trophic level

Question 18

pesticides

1962: Silent Spring (Rachel Carson)

Answer 18

Uncontrolled pesticide use leads to the deaths of not only animals, especially birds, but also humans.

Question 19

pesticides effects

Answer 19

Pesticide use has increased 50-fold since 1950, and 2.5 million tons of industrial pesticides are now used each year
Pesticides are transported to the Wadden Sea by the North Sea currents
Bioaccumulation in common seals lead to a drastic decline in birth rates in the 1970s-1980s

Question 20

DDT

Answer 20

1945: large scale introduction of DDT
1948: Nobel prize for Müller, who discovered DDT
mallard eggs get contaminated by DDT shell walls break down, really bad for brachiopods
1970-1972: DDT is banned by most governments
Objections from some entomologists and farmers: DDT has saved millions of lives (less malaria)

Question 21

Agriculture in the Netherlands

Answer 21

107 million chickens living in Dutch chicken farms (source: CBS, 2015)
12.6 million pigs living in Dutch pig farms (source: CBS, 2015)
On average 5900 pigs per farm

Question 22

Maximum sustainable yield (MSY)

Answer 22

The maximum crop or yield that can be removed repeatedly from a population without driving it towards extinction.

Net recruitment is maximal at intermediate densities
MSY = maximum net recruitment

Question 23

MSY can be obtained through:

Answer 23

Fixed quota Fixed effort

Question 24

Fixed quota

Answer 24

do not take natural fluctuations into acount Disasters may happen

Question 25

Fixed effort

Answer 25

leads to fluctuations in the annual catch Risk of extinction is much lower E.g. the lobster season in Zeeland lasts from 1 April to 15 July

Question 26

Other fisheries management options:

Answer 26

Sparing small undersize individuals Sparing large mature individuals Marine protected areas (MPA’s) No-fishing periods