D4.2 - sustainability of ecosystems (1i)

Question 1

what are resources?

Answer 1

both living and non-living materials that are harvested and used by humans

Question 2

what makes a resource renewable?

Answer 2

renewable resources can be replenished at an equal or faster rate than it is being used

Question 3

what is sustainable agriculture?

Answer 3

the goal of sustainable agriculture is to meet the food and textile needs of the world’s population today, without jeopardizing the ability of future generations to meet the same needs

Question 4

what does sustainability depend on in terms of agriculture?

Answer 4

sustainability depends on the rate of harvesting being lower than the rate of replacement

Question 5

how can sustainability of harvesting be assessed using black cherry trees?

Answer 5

• this light red-coloured hardwood is sought after for furniture
• in the allegheny national forest (USA) the relative abundance has fallen from 25% in 2004, to 4% in 2019

Question 6

what unsustainable practices were being carried out using black cherry trees?

Answer 6

• random selection of individual trees within the target species
• clear-cut logging, where all trees and vegetation is cut to ease the removal of target trees from an area

Question 7

how does the forest stewardship council regulates and certifies sustainable logging practices?

Answer 7

• data is collected to ensure the rate of regrowth is equal to or faster than the rate of removal
• individual trees are identified and removed using selective logging, without removing the surrounding trees
• enough trees are left to produce fruit and seeds for the next generation

Question 8

how can sustainability of harvesting be assessed using atlantic cod?

Answer 8

• in 1992 cod populations fell to 1% of historical levels, due to overfishing with the development of technology that was more efficient at landing the fish
• the marine stewardship council is an international group that assesses fishery practices and awards certification to those that have sustainable practices

Question 9

what unsustainable practices were being carried out using atlantic cod?

Answer 9

• overfishing - when too many fish in a particular stock are caught and there are not enough adults to breed and sustain a healthy population
• unregulated fishing activities - when fisheries do not have or do not act on quotas to regulate the size of their catch
• excessive ‘unwanted catch’, which is undersized or surplus fish that fisheries do not have a quota for, as well as endangered, threatened and protected species, and other unwanted marine species

Question 10

what are examples of sustainable practices when harvesting cod?

Answer 10

• working out how many fish can be safely caught without impacting the future health of the stock
• prohibiting fishing during spawning seasons and setting size limits to allow juveniles to escape, are management techniques to protect stocks from overfishing
• adopting harvest control rules, which require catches to be reduced if the stock population declines

Question 11

what factors are affecting the sustainability of agriculture?

Answer 11

• soil erosion
• leaching of nutrients
• supply of fertilizers and other inputs
• pollution due to agrochemicals
• carbon footprint
• removal of nutrients by harvesting agricultural crops

Question 12

why are agricultural areas less sustainable than natural ecosystems?

Answer 12

• have a lower biodiversity
• are more affected by pests and disease
• have less efficient nutrient recycling, as nutrients are removed when crops are harvested, so there is less organic matter in agricultural soils, which may become infertile
• have less transpiration and so less water recycling
• have less biomass and carbon stored

Question 13

what is the process of eutrophication?

Answer 13

high concentrations of nitrogen or phosphate in water causes eutrophication:
1. the high concentration of nitrogen or phosphate causes algae to multiply rapidly, called an algal bloom
2. the algae die and are decomposed by bacteria
3. additionally algae do not let light go through the water, so less photosynthesis is possible for the aquatic plants, and they die
4. decomposers consume oxygen from the water, leading to an increased biochemical oxygen demand (BOD) and hypoxia
5. if oxygen levels drop too low, fish and other aerobic aquatic organisms die, decreasing biodiversity

Question 14

what is leaching?

Answer 14

leaching is where excess rains, floods or irrigation can wash away nutrients from soils into groundwater, lakes, streams or oceans
- leaching of nitrogen and phosphate fertilisers can lead to eutrophication

Question 15

what causes excess nitrates or phosphates in an aquatic ecosystem?

Answer 15

• natural run-off
• erosion of rocks
• sewage release
• fertiliser run-off

Question 16

what are the effects of eutrophication?

Answer 16

• high net primary productivity, due to the algal bloom
• low water visibility
• reduced biodiversity

Question 17

what is rewilding?
how does it differ from other active management techniques?

Answer 17

rewilding is a conservation approach that restores and protects natural processes and wilderness regions
- differs from active management techniques, as the areas are left to nature with successful projects requiring little ongoing human attention

Question 18

what are the different methods of restoring natural processes in ecosystems by rewilding?
how would each of these techniques contribute to a rewilding project?

Answer 18

reintroduction of apex predators and other keystone species to create a self-regulating and self-sustaining ecosystem
- to create a self-regulating and self-sustaining ecosystem

re-establishment of connectivity of habitats over large areas
- increasing availability of food resources
- facilitating the re-establishment of populations after catastrophic events
- maintaining genetic diversity and preventing the negative effects of inbreeding

minimization of human impact including logging, hunting and ecological management
- prevent removal of habitats and food sources
- prevent disruption of food chains and webs

Question 19

what is an example of a rewilding project?

Answer 19

an example of a rewilding project is the hinewai Reserve in new zealand
- it was created in 1987 with 109 hectares of ex-farmland, before being expanded to 1,250 hectares
- minimal intervention was used to remove a few invasive species, but generally nature is left to run its course, most likely to majority forest cover, with human interaction limited to publicly accessible paths
- while still a work in progress, the goal is for native vegetation and animals to repopulate the area