Chapter 13- Maintaining Biodiversity Flashcards
What are the factors that affect biodiversity
Human population; the threats are:
Habitat destruction and degradation of the environment
Overexploitation and unsustainable use of resources
Modern agricultural practices, including monoculture, the use of chemical fertilisers and crop protection chemicals
Global climate change
What is habitat destruction
Destruction of the natural environment leads to habitat loss
Habitat fragmentation occurs when the habitat of the species of plants and animals get divided into small areas. Populations subdivided by this process are in danger of local extinction and inbreeding (Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically.)
Reasons of habitat destruction would be for: agriculture; industry; housing; transport; leisure facilities; waste disposal; water storage
Habitat destruction is occurring more rapidly in tropical rainforests, tropical dry forests and savannahs
What is deforestation
Clearing of large areas of plants
Roots bind soil particles together and absorb much of the rainfall. When forests are taken away, water tends to run straight off the land leading to flooding.
Therefore, deforestation can lead to severe land degradation as a result of soil erosion and loss of soil nutrients
Ex: Madagascar has now lost most of its natural forest even though it was once famed for its unique plants and animals.
Vast forests in South-East Asia, Africa, Amazonia and South America have been cut down to be replaced with cattle ranches and plantations of oil palm.
Causes of the loss of marine ecosystem
Dynamiting coral reefs- an extreme way to catch fish
Fishing by using trawl nets that are pulled across the sea beds- due to this, very little of the natural ecosystem in the North Sea is left
Dredging of coastal waters and development along coastlines for industry, housing and tourism
Removal of trees, ploughing and the run-off from roads and urban areas increasing the sediments in rivers that flow into coastal waters.
Examples of overexploitation
Cutting down slow-growing trees such as mahogany, timber and teak at a faster rate than they can regenerate.
The species, Atlantic cod, Gadus Morhua, collapsed in the 1990s due to overfishing, declining over 95% of their maximum historical biomass. These stocks of cod have failed to recover even after no fishing.
By removing large predatory fish such as cod, less food is available for larger fish, marine mammals and seabirds thus further loss of biodiversity
By removing large predatory fish such as cod, less food is available for larger fishes, marine mammal and seabirds- thus further loss of biodiversity.
How did the fish industry respond to the declining biomass of cod
They started to target smaller fish further down the food chain (lower trophic levels)
Fishing at lower trophic levels at first to an increase in catches and then to declining catches. This shows that the present exploitation of many fish stock is unsustainable.
How does hunting affect biodiversity
In poor countries, there is a trend for hunting bush meat. Due to this, animals such as monkeys, chimpanzees, many other species of mammals and reptile are at risk. The development of roads into forests for logging has made larger areas available for hunting.
Plants are removed from their habitat for sale or as food. The wild populations of African Violet, Saintpaulia, a very common cultivated plant, are dangerously low as a result of it being collected from the wild.
Examples of intensive farming practices
Planting the same crop year after year
Using large machinery for cultivation and harvesting
Employ few people and guarantee large yields per hectare.
Use of fertilisers, crop protection chemicals and fossil fuels (for powering machines)
What is monoculture
intensive arable (fertile) farming is a type of monoculture.
Is used for livestock farming where many animals of the same species are reared together, often in semi-industrial units.
Same plant planted in a large area close together, because of the high demand of its product; e.g : coniferous trees to provide softwood and paper pulp are monocultures; so is oil palm plantations in the tropic.
Clearing up large lands of natural vegetation for rearing cattle is also monoculture
Why is monoculture practiced
Allows farmers to cultivate land more efficiently, so less land is required than when farmers mixed arable crops and livestock and when wastage was much higher.
However monoculture has much less biodiversity
How does monoculture affect biodiversity
Reduces biodiversity
Since growing the same crop year after year exhausts the supply of minerals in the soil; the farmers replenish these with high inputs of chemical fertilisers.
Crops need constant supply for water thus increasing the demand of water
Farmers also use herbicides to eliminate the plants that compete the crops for resources.
Pesticides such as fungicides are also used to tackle fungi, bacteria and viruses
Why is monoculture disadvantageous
Pests such as boll weevils and aphids increase exponentially when environmental factors are favourable in monocultures
This is because the crop provides an unlimited supply of food
Who do insecticides do
Controls the food insects
Why are fertilisers bad
These make the soil nutrient-rich; encourages growth of some plants, which shade out slower growing plants, depriving them of light
Why are herbicides bad
Kills weed that compete with the crop for resources and maybe the source of pathogens and pests of crop plants
While being sprayed, can also kill many non-target species, thus reducing biodiversity
Why are insecticides bad
Kill insect pests.; also kills non-target species that may not have any negative effects on the crop.
These maybe the predators or parasites of pest species. Insects that are important for pollination may also be killed.
The insecticide may persist in the soil and then kill the detrivotes.
Other causes of the loss of biodiversity
Removal hedges, small areas of woodland and scrub to make larger fields- removes nesting sites
Ploughing right up to the edges of fields thus removing the habitats of many plants and insects
A reduction in habitat structure and diversity- some bird species associated with farmland prefer tussocky grass species that are not favoured by livestock farmers
Improved methods for cleaning crop seeds- reducing the chances of weed seeds being resown
Loss of wild food plants for insects such as butterflies and hoverflies as a result of herbicide use
Conversion of pasture to arable land and the resultant decline in soil invertebrate numbers- less food for for farmland birds and mammals.
Land drainage causing the soil invertebrates to live deeper in the soil, so making them less accessible to birds and mammals
Sow cereal crops in the autumn instead of leaving stubble in the ground until spring; reduced the availability of food for bir and mammal species.
Pollution of argiculture:
Fertilisers
Pesticides
Waste products from intensive livestock production
Fertilisers are applied to crops to increase their yield
Problem with fertilisers
Adding too much, or adding this after heavy rain, can result in the fertiliser draining from the land into the rivers and lakes.
Can cause water pollution and eutrophication (waters are enriched with plant nutrients)
Nitrate ions that run off by arable land can cause algae bloom in the sea.
These run off fertilisers also cause huge growth of plankton; which are consumed by bacteria and deplete the waters of oxygen.
E.g the Gull of Mexico has a 22 000 square kilometre ‘dead zone’ every spring due to run off from the Mississippi River.
400 areas in oceans are starved of oxygen due fo this; the number is growing.
Pesticides cause the selection of resistant strains of weed and insect pests.
The pesticide DDT was responsible for eggshell thining and poor reproductive success in falcons.
What about climate change
the climate has always changed, with ecosystems changing and species evolving and becoming extinct.
This change is occurring very fast and are likely to be too fast for species to adapt.
A modification of weather patterns, and an increasing number of extreme weather events such as hurricanes, typhoons, floods and droughts
The distribution of many species is changing- they are moving towards the poles and to higher altitudes and latitudes. They are not well adapted for the new ecosystem and are in competition of better adapted animals.
Climate change causes Artic ice caps to melt which may lead to the loss of an entire biome; this also harms the algae living on the underside of the ice, which are the producers of this ecosystem
Low pH of the sea water- CO2 is very soluble in water. More CO2 in the atmosphere; more dissolved in water of the oceans; lower the pH of the ocean
The low pH makes it difficult for organisms to make shells of calcium carbonate; such organisms include tiny planktonic creatures that have shells, and coral polyps, some of which make coral reefs. The calcium carbonate of the organisms’ skeletons acts as a ‘sink’ for carbon, which lasts millions of years. If this activity decreases, then less CO2 is taken out of the atmosphere and into these long term storage.
Ocean acidification threatens the survival of coral reef.
Warming of ocean water is likely to cause, stratification, so that surface waters will not mix with nutrient-rich water from deep in the ocean. If this happens, the phytoplankton- the main producers of the sea- will not grow and provide food
Why should we maintain biodiversity in terms of ecological
The loss of species leads to an imbalance in natural communities. Higher biodiversity means higher stability and therefore are able to withstand environmental changes.
Are also able to recover more rapidly and more thoroughly after environmental damage.
Therefore high biodiversity-> high resistance and high resilience
The loss of predatory groups such as lions, tigers and leopards will lead to an increase in the population of herbivores. This will be lead to overgrazing, land degradation, erosion and loss of biodiversity.
What are keystone species + example of why they are needed
A species whose presence contributes more to the function of an ecosystem than its size or number suggests. Without these species, biodiversity decreases, and the ecosystem becomes unstable.
The loss of sea otters from the Pacific Coast of North America by overhunting removed an important predator for sea urchins, which feed on kelp. This resulted in a devastation in the number of kelp forests and the species associated with kelp. Therefore sea otters are a keystone species
