D4.2 Stability & Change Flashcards

Question

What are the advantages & disadvantages?

Answer 1

Keystone species = one whose activity has a disproportionate effect on structure of an ecological community. Could be predator e.g. wolf or

Answer 2

American Beaver (Castor canadensis) = example of a keystone species in North America. Beavers perform unique and crucial roles within an ecosystem - functions that would be substantially different or non-existent without them.

Answer 3

Sustainability = responsible maintenance of ecological systems so that there is no reduction of conditions for future generations, ensuring long-term viability of a system. Sustainability depends on rate of harvesting being lower than rate of replacement.

Answer 4

Forests have played an important role in Finnish history. Finnish forests have provided food, shelter, employment + income for Finns through centuries. Forest Act provides a framework for forest management in Finland. Leading principle of forest legislation has been obligation to regenerate after logging.

Answer 5

Black cherry is a species of hardwood tree, found in N America, that is popular for furniture production. Hardwood tree species grow slowly, so it is especially important that sustainable harvesting methods are used; methods such as clear felling will leave no timber for many years to come. Sustainable harvesting of black cherry timber involves: - Selective felling; choosing specific individual trees to harvest, leaving gaps in the forest canopy that will encourage growth of more plants on forest floor - Leaving enough individuals behind in the forest to flower & produce seeds, ensuring that new black cherry saplings will germinate - Regular monitoring to ensure that new growth is keeping up with logging

Answer 6

Many fish, such as the Cod (Gadus morhua) of N Atlantic, are on verge of extinction – with most probably cause being overfishing. Rapid decline of many fish species & difficulties associated with international conservation programmes make sustainability goals more & more important.

Answer 7

If pop of fish are persistently overfished (as regularly are), stocks will be rapidly depleted to point where they collapse & can no longer support a commercial fishery. Extent to which species are fished should be based on pop dynamics that consider their reproductive & growth rates. Pop size & age structure can be used to inform practices associated with sustainable fishing.

Answer 8

Pollock are a species of fish found across N Pacific. Alaska pollock fishery is largest sustainably certified fishery in the world. This certification is awarded by Marine Stewardship Council (MSC). Fishery is considered to be sustainable because Pollock are a fast-growing species which can reproduce from the age of 3-4 years and nets have minimal contact with the sea-bed, so do not damage this habitat. The proportion of fish caught that are not pollock, known as bycatch, is very low; less than 1 % & according to regulation, any bycatch that is caught cannot be sold commercially, so it is in interest of fishermen to avoid catching it. Close monitoring is carried out by science research vessels & by trained individuals on board commercial fishing vessels. Any areas where a higher than normal number of salmon bycatch occurs are closed off to fishing vessels.

Answer 9

- Precipitation (type, frequency, intensity, amount) - Temp (growing season (>6°C), ground frozen (0°C), range of temp) - Soil (fertility, nutrient status, structure, texture, depth) - Pests (vermin, locusts, disease) - Location (slope gradient, relief, altitude, aspect – shady or sunny)

Answer 10

- Soil erosion – this is caused by tillage, which involves plowing, harrowing & results in a reduction of soil quality. - Fertilisers : Growing crop causes nutrient depletion over time which needs fertilizers (agrochemicals) to compensate. Excess amounts of nitrogen & phosphate containing fertilizers leach into water systems potentially leading to eutrophication. - Leaching: soil exposure can lead to leaching of nutrients from soil. When it rains, nutrients are washed away & not available anymore for plants. - Carbon footprint: use of heavy machines for tillage, harvest, transport needs a lot of energy & produces large amounts of carbon emissions (diesel engines). Glasshouses & stables for animals need heating & further contribute to this. - Monocultures: repeated growth of same crop results in pests & weeks to become increasingly problematic. Use of pesticides & herbicides can cause pollution problems & production of chemicals needs energy.

Answer 11

In order to grow crops or keep large numbers of grazing animals, land needs to be cleared to make space for crops or grass. Removal of larger trees & shrubs means that roots that hold soil together are lost, resulting in less stable soil that can easily be washed or blown away. This is a particular risk for nutrient-rich upper soil layer, known as topsoil. This leads to soil erosion, & a reduction in availability of soil needed for crop/grass growth. While crops & grass themselves can aid soil stability, they may only provide partial cover, or they may be removed after harvest, or due to overgrazing/poor weather. Farmers sometimes plant 'cover crops' to hold topsoil together in between growing seasons.

Answer 12

Use of synthetic fertilisers in agriculture can lead to nutrient runoff due to leaching. This occurs when rainfall washes fertilisers out of soil & into nearby bodies of water. Minerals in synthetic fertilisers are highly soluble so dissolve in rainwater before being washed away. Problem of leaching can be reduced by applying fertilisers in small volumes, at times when rain is not forecast, & by using organic rather than synthetic fertilisers

Answer 13

Chemical fertilisers are important for many farmers, but they are not always easy to supply. They are expensive. They are used by many farmers, so supply may not meet the large demand. Process of fertiliser production is very energy intensive, so cost of fertilisers is affected by global energy prices. Switching to organic fertilisers can help to reduce some of difficulties associated with chemical fertiliser use.

Answer 14

Some types of farming rely on use of chemicals, known as agrochemicals. Additional examples of agrochemicals include: - Pesticides - Herbicides - Fungicides These chemicals are used to improve yield, which might otherwise be damaged by insect pests, competition from weeds, or by fungal disease. These chemicals can enter natural environment & cause problems, e.g. by killing non-target species. Biological pest control can reduce pesticide use. This involves release of a pest's natural predators, e.g. ladybirds that prey on aphids. Scientists hope that genetic modification may allow introduction of crop varieties that are resistant to pests & disease.

Answer 15

Reliance on fossil fuels for transportation, machinery, & productionof synthetic fertilisers has significant implications for sustainability of food production Combustion of fossil fuels releases carbon dioxide into atmosphere, increasing carbon footprint of agriculture & contributing to climate change. Transitioning to renewable energy sources & promoting energy-efficient practices can help reduce carbon footprint of food production.

Answer 16

- Natural effects include nutrients being added from decomposing biomass & run-off from areas surrounding body of water. Eutrophication can occur naturally through gradual drying up of pools of water & disproportionally increasing amount of nutrient rich sediment. - Human causes include run-off of fertilisers or manure from agricultural land, domestic waste water containing phosphates from detergents, & non-treated sewage. Usually eutrophication is due to leakage of excess chemicals used in agriculture (fertilisers) which contain nitrogen and phosphates. - Leaching of mineral nutrients from agricultural land into rivers can also cause eutrophication.

Answer 17

Eutrophication is referring to the excessive nutrient enrichment of water. Nutrients such as phosphates & nitrates favour growth of algae, which multiply in great numbers & lead to algae bloom. Raised temp in the Summer months add to algal growth rates. Algal blooms form a thick, sunlight-blocking cover on surface of the water. This prevents oxygen from dissolving & also photosynthesising plants on ground from carrying out photosynthesis so they die. Decomposition by bacteria further depletes oxygen supplies.

Answer 18

Amount of dissolved oxygen required to break down organic material in a given volume of water through aerobic biological activity can be measured by BOD (biological oxygen demand).

Answer 19

Aerobic organisms use oxygen in respiration. With more organisms & faster respiration, more oxygen will be used thus resulting in a higher BOD. In aquatic systems with organic pollution (e.g. sewage, fertilizers etc) pop of organisms that feed on or use nutrients in pollutants increases. BOD therefore indirectly measures pollution.

Answer 20

BOD is an indirect method to determine water quality & aerobic activity by bacteria. It's determined by taking a measured volume of water from a source (e.g. pond, stream etc) & measuring the dissolved oxygen content on Day 1 in mg/L using an oxygen probe. Sample is then placed in dark (to prevent photosynthesis) at 20°C for 5 days. After 5 days oxygen level is measured again. BOD is difference between initial & final Oxygen conc.

Answer 21

BOD levels are dependent on body of water being tested. Shallow, slow-moving waters, such as ponds & wetlands, will often have large amounts of organic material in water & high BOD levels.

Answer 22

Polluting chemicals from human actions seep into food chains of many organism. Pollutants might only be released in very low concentrations, but at higher end of a food chain an organism might have accumulated almost lethal dosages.

Answer 23

Increase in conc of a toxin in body tissues during an animal’s lifetime. Usually this happens with fat soluble chemicals which cannot be excreted (e.g. mercury compounds). It occurs over time, only one particular animal life type.

Answer 24

Increase in conc of a chemical at each successive trophic level in a food chain. Predators tend to accumulate higher chemicals of a toxin than their prey because larger quantities are consumed. (Along a food chain)

Answer 25

- Biomagnification = increase in concentration of persistent or non-biodegradable pollutants with ascending trophic level through a food chain - Not to be confused with bioaccumulation, which = build-up of pollutants within an organism, or within a single trophic level

Answer 26

As pollutants are passed up food chain from one trophic level to the next, they can become more concentrated due to decrease in total biomass of organisms at higher trophic levels. I.e. smaller organisms at bottom of food chain will each consume a small volume of pollutant, & then organisms at top of food chain will consume many smaller organisms and receive a much larger dose of pollutant.

Answer 27

- Mercury is released into environment through activities such as coal-fired power plants & gold mining. - Once in environment, mercury can be converted by microorganisms into a highly toxic form called methyl mercury, which can accumulate in bodies of fish. - As larger fish eat smaller fish, conc of methyl mercury within tissues of these fish increases, leading to potential harm for humans who eat large predatory fish e.g. swordfish, shark, mackerel, cod, bluefin tuna (especially during pregnancy).

Answer 28

Toxins such as DDT (dichlorodiphenyltrichloroethane) are persistent pollutants that can enter food chains DDT was a widely used insecticide in mid-20th century that was found to have harmful effects on top predators such as birds of prey.

Answer 29

When DDT was sprayed on crops, it would leach into waterways & eventually enter freshwater & marine ecosystems. DDT would then enter food chains via plankton & accumulate in bodies of fish. These fish would then be eaten by birds, which would accumulate higher concentrations of DDT. Bc DDT is persistent & doesn't break down easily, it can continue to accumulate in bodies of animals at higher trophic levels, leading to harmful effects such as thinning of eggshells & reduced reproductive success. Thin eggshells couldn't withstand weight of parent bird during incubation, so eggs would break & fewer young birds would hatch. Over time this resulted in reduced bird pop. DDT has now been banned worldwide, with exception of its use in areas where it is essential in dealing with mosquitos that transmit malaria.

Answer 30

- Plastics describe a range of polymers which are mostly non-biodegradable. - Plastics are used in an increasing number of consumer products. - Plastic waste in oceans is a big problem. - Marine animals mistake plastics for food & often suffocate or become entangled in floating materials.

Answer 31

- Macroplastics (large, visible, more than 5mm in size e.g. bottles, plastic bags which can be confused with food by marine predators) - Microplastics (extremely small pieces of plastic debris, less than 5mm resulting from breakdown of consumer products & industrial waste)

Answer 32

- Microplastics & their non-biodegradable contaminants can bioaccumulate in food chains. - Predators in higher trophic levels are often at extra risk because of biomagnification effects of some chemicals. - Abundance of macro & microplastics has been steadily increasing.

Answer 33

- Animals often try to eat plastic, e.g. Turtles may attempt to eat a plastic bag that resembles a jellyfish. Plastic garbage harms & kills or Albatrosses may accidentally consume plastic when they fish, giving it to their chicks when they regurgitate food; chicks may later starve due to their stomachs being full of plastic - Animals become caught in plastic, such as fishing lines, leading to injuries and death - As plastic breaks down it can release toxins that can lead to biomagnification in food chain - Once it has broken down into very small particles, it's commonly ingested by animals & enters food chain

Answer 34

- Laundering synthetic textiles - Manufacturing using polymers - MPs in treated wastewater - MPs in biosoilds -MPs in stormwater runoff - Trash disposal/littering - Erosion - Dust from amended soil - Plastic trash degradation - Dust settling/stormwater runoff -Plastic degradation/stormwater runoff - MPs in salt spray - Point degradation - Plastic fishing gear - Maritime accidents

Answer 35

Ecosystem degradation by human actions has caused severe consequences such as loss of biodiversity, species extinction & loss of ecosystem services such as flood protection, carbon sequestration & climate regulation.

Answer 36

Efforts are being made to encourage natural ecosystems to return. One approach is rewilding.

Answer 37

Rewilding aims to restore ecosystems and reverse declines in biodiversity by allowing wildlife & natural processes to reclaim areas no longer under human management. Rewilding is all about returning land and oceans to a more natural state. This is often done by doing nothing.

Answer 38

- Rewilding reintroduces lost animal species to natural environments, such as top (apex) predators that have a significant effect on food web & trophic levels in an ecosystem. - Keystone species are also reintroduced, which are essential for functioning of the ecosystem. - Establishment of connectivity of habitats over large areas, using corridors of habitat that connect different areas, allows for movement of animals between fragments & gives larger animals area they need to feed and breed. - Agriculture & other resource harvesting are no longer allowed & natural ecosystems are allowed to recover through ecological management.

Answer 39

- Hinewai Reserve is an ecological restoration project on Banks Peninsula, New Zealand. - It was once farmland, but is now privately owned, with aim of restoring natural ecosystem of area - Some initial human intervention was involved, with removal of non-native species (alien species such as exotic trees and vines), but area is now managed with minimal human intervention to allow native communities to be restored by succession - Human activities are limited in area, though public can enjoy walking in Reserve

Answer 40

- Distributing seeds of plants (endemic species) - Reintroduction of apex predators (e.g. wolves or beavers) & other keystone species - Re-establishing connectivity between fragmented parts of an ecosystem. - Control of invasive alien species - Removal of livestock (cattle, goat, horses etc)

Answer 41

All ecosystems develop over time from point of colonisation of a pristine area to maturation of a stable final community. This is caused by ecological succession. Succession is orderly process of change over time in a community.

Answer 42

Succession usually starts with a pioneer community (1st community), goes through a range of intermediate stages & finishes with a climax community (final stage).

Answer 43

Succession can be triggered through changes in abiotic factors such as: - changes in water availibility (e.g. bc of changed weather patterns), - temp - soil composition, - natural disturbances such as floods, fires, vulcanic eruptions etc.

Answer 44

Biotic factors such as changing relationships within food chains can also trigger succession. Changes in community of organisms frequently cause changes in physical environment, allowing another community to become established & eventually replace former through competition. Often, but not inevitably, the later communities in such a sequence (or sere) are more complex than those that appear earlier.

Answer 45

1. Succession in freshwater: aquatic plants -> reeds -> low woodland species 2. Succession in an abandoned quarry: mosses and lichens -> grasses & herbs -> shrubs -> woodland

Answer 46

A pioneer community is 1st stage of an ecological succession that contains hardy species able to withstand difficult conditions with little nutrient availability. E.g. mosses, fungi, lichen, bacteria.

Answer 47

A climax community is a community of organisms that is more or less stable an equilibrium with natural environmental conditions such as climate. It is end point of ecological succession. It includes large trees & dense forests & complex interspecific relationships.

Answer 48

Primary succession start with a pioneer community, then goes through stages of intermediate communities, & finally succession ends with a climax community.

Answer 49

There are two types of succession – primary & secondary.

Answer 50

Primary succession begins with a completely barren environment with very early colonizers generating small amount of growth on which more & more communities develop.

Answer 51

Secondary succession occurs where a disturbance has cleared away an existing community but leaves the soil intact.

Answer 52

Primary succession begins in an environment were living organisms are largely or completely absent. Mostly, this is bare rock or gravel, deposits of silt or clay. Nutrient rich soil is usually not present.

Answer 53

A xerosere = succession under dry, exposed conditions where water supply is an abiotic factor limiting growth of plants (at least initially).

Answer 54

With the arrival of pioneer species small amounts of soil can form allowing herbs with roots to start to grow. With deeper soil species diversity increases & more species join than are eliminated. Primary production increases & complex foodwebs can form with nutrient cycling ensuring sustainability.

Answer 55

1. Pioneer species arrive (e.g. lichens, mosses & bacteria) 2. As pioneers die, soil is created 3. New species of plants arrive that need soil to survive – these displace pioneer species 4. Growth of plants causes changes in environment (e.g. light, wind & moisture) 5. Growth of roots enables soil to be retained, nutrients & water in soil increases 6. Nitrogen-fixing plants arrive, adding nitrates to soil 7. Soil depth increases further, allowing shrubs & other taller plants to arrive 8. Animal species arrive as species of plants they rely on become established 9. A climax community is established.

Answer 56

- In pioneer communities, gross productivity is low due to initial conditions & low density of producers. Proportion of energy lost through community respiration is also relatively low. Net primary productivity (NPP) is therefore high: system grows and biomass accumulates. - Gross primary productivity increases due to increase in biomass of community. Sunlight is available for all plants as there is little shading. - In later stages there is an increased consumer community, with increased levels of respiration, leading to a reduction of NPP. Rate of accumulation of biomass begins to slow. - In climax communities gross productivity may be high, but this is balanced by community respiration & so overall NPP may be lower than earlier in succession.

Answer 57

- Size of plants increases through a succession, & complexity of food webs also increases. - Nutrients initially come from outside the succession in pioneer stages, but through succession, with increases in biomass, soil depth & complexity, nutrient cycling within ecosystem becomes increasingly important. - With increased complexity of ecosystem during succession, there are increased opportunities for a variety of diff niches & so species diversity increases. - Nutrient availability changes from poor initial stores through to gradual accumulation of nutrients as biomass develops & soil fertility increases.

Answer 58

- Sometimes ecosystems experience a cycle of change rather than a stable climax. - Species replace each other over time repeatedly without very large disturbances. - Dominating climax communities are regularly replaced by other ones.

Answer 59

An example of cyclical succession can be seen in grazed woodlands, which can contain a changing mosaic of grassland, woodland, & scrub This habitat can be described as wood pasture as farm animals or deer are systematically grazed on tree land. In a grazed wood pasture, following cycle of events can be observed : - Grazers, such as cattle, graze on pockets of open grassland within a woodland, where they consume tree seedlings and prevent growth of trees - Fast-growing thorny species, such as brambles, may arise in some areas within the grassland, creating a mosaic of thorny scrub - Tree seedlings can survive within thorny vegetation, which deters grazers - Trees grow up through thorny scrub, which will eventually fail to get enough light through tree canopy & die off - At end of its life tree dies & falls, creating an open area where grass can grow, & restarting cycle

Answer 60

- Regular fire cycles in Australian bush lead to continous replacement of climax communities. - Bushfires occur every 10 – 15 years on a regular pattern. - Some of 1st plants to regrow are grasstrees (Xanthorrhoea australis). - These plants often flower as a direct result of fire, quickly bringing an essential food source to surrounding birds, insects & other wildlife. - It's often 1st spurt of colour in an otherwise blackened environment.

Answer 61

Honeycomb barnacles (Chlamaesipho columna) growing on the rocky shore of the North Island of New Zealand follows a cyclic pattern of succession. 1. Honeycomb barnacles attach to bare rock 2. Crustose algae (Ralfsia confusa) colonizes 3. Black mussels (Xenostrobus pulex) settle on top 4. This smothers the barnacles and algae underneath 5. Mussels detach, bare rock becomes available again.

Answer 62

Given any specific environmental conditions (climatic and edaphic – soil), ecological succession tends to lead to a particular type of climax community.

Answer 63

1. They contain more complex food webs (this provides more stability because, if 1 organism becomes extinct, it can be replaced by another) 2. Negative feedback mechanisms lead to steady-state equilibrium 3. Each stage in succession helps to create a deeper & more nutrient-rich soil, so allowing larger plants to grow 4. A climax community is more productive, providing more energy to support consumers & decomposers 5. Increased biomass leads to an increased number of niches, which increases species & genetic diversity, resulting in greater stability.

Answer 64

With the progression of succession, the pace of change slows down and eventually a climax community exists until a disturbance causes another change. Sometimes human activity alters the natural process.

Answer 65

Interrupted succession is known as arrested succession or plagioclimax.

Answer 66

1. Reduction in productivity through removal of primary producers 2. Reduction in producers, leading to reduced habitat diversity & fewer niches, which threatens more specialised species 3. Deterioration in abiotic factors, leading to harsher conditions that fewer species can adapt to 4. Species extinction, leading to shorter food webs 5. A less complex community, leading to decreased stability. These activities divert progression of succession to an alternative stable state so that original climax community is not reached.

Answer 67

Two examples of this so-called plagioclimax are pastoral grazing & wetland drainage.

Answer 68

- Pastoral farming involves cattle, sheep or other animals on pasture, which are protected from predation & which continuously feed on grasses. - Small plants of trees & seeds of shrubs are regularly removed that way, never being able to develop into trees & forests of a climax community.

Answer 69

- Swamps & wetlands are specialised ecosystems with many plants & animals adapted to anaerobic conditions in soil. - Wetlands often accumulate peat. - Drainage is often performed to make these areas habitable for crops, housing or for extraction of peat. - Soil dries out changing ecosystem considerably.