10.3 species diversity and human activities

What are natural ecosystems?

Natural ecosystems develop over time become complex communities with high index of diversity

What are agricultural ecosystem ?

Controlled by humans

* species are selected
* Reduced number of species and genetic variety of alleles
* Increased number of desirable species affects biomass
* Many competitions between species (light)
* Use of pesticides to exclude other species
* Reduction of species diversity

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What is conservation ?

Concept of preservation /maintenance

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Aims of biological conservation

* to maintain diversity
* To maintain organisms habitats /ecosystem

What are conservation schemes?

* legal protection to endangered species
* Creating protected areas such as SSSIs (Sites of Special Scientific Interest)
* Encourage farmers to replant hedgerows and allow wildflower borders along field edges

what practices have reduced species diversity

* removal of hedgerows
* creating mono-cultures
* filling in ponds and draining marsh
* over grazing of land

what practices have had a more indirect effect?

* use of pesticides and inorganic fertilizers
* escape of effulant from silage stores
* absence of crop rotation and lack of inter cropping

what are some conservation techniques ?

* maintain existing hedgerows at the most beneficial height and shape
* maintain existing ponds
* plant native trees on land with low species rather than species rich areas
* reduce use of pesticides
* use crop rotation including a nitrogen fixing crop,rather than fertilizers to improve soil fertility
* use inter cropping rather than herbicides to control weeds and other pests

Explain how monoculture is used in agriculture.

* involves the rowing of a single crop in an area more water, mineral ions, carbon dioxide pesticides can be used to reduce number of pests that damage crop plants.

Explain the disadvantages of monoculture

* pesticides could kill beneficial animals costly
* - need to maintain the environment and monitor number of other organisms
* if any pests do survive, then a monoculture enables them to spread rapidly

How does removing hedgerows reduce biodiversity?

* Smaller fields are made into one larger field .
* This destroys habitats Biodiversity is reduced as habitats and food sources are removed

How does the clearing of woodlands reduce biodiversity?

* The number of trees, and the number of species of trees are both damaged .
* This means habitats are destroyed.
* The land is used for farming, but it means the species living there cannot use it for shelter and as a food source, particularly if pesticides are used
* The species must migrate or die

How does the use of pesticides reduce biodiversity?

* These are chemicals used to kill the organisms that feed on crops - known as ‘pests'
* The pests are killed, and biodiversity is reduced
* Species that prey on the pests lose food sources, so their species numbers could also fall

How does the use of herbicides reduce biodiversity?

* These are chemicals used to kill the unwanted plants .
* The plants are killed, and biodiversity is reduced .
* Species that prey on the plants lose food sources, so their species numbers could also fall

How does mono culture reduce biodiversity?

* Growing only one type of plant, perhaps because it has high sale demand for food.
* Biodiversity is directly reduced by doing this, particularly is other plants that are natural to the area are killed and removed to make space .
* Also, fewer organisms can be supported.

Importance of Species Diversity

The species diversity can be
used as a measure of health of
an ecosystem

The higher the species
diversity index the more stable
and ecosystem is likely to be

Impact of Agriculture on Biodiversity

Agriculture reduces species diversity

* Less species=

Each area can only
support a limited amount
of biomass – if there are
lots of one species, there
will be less variety of
species
* Less alleles within a species=

Species are often selected
based on desirable
characteristics to make
farming more productive,
this results in less genetic
variation

Explain how agriculture has reduced species diversity (3)

The desired species makes up a lot of the biomass in the area,
reducing availability for other species

Selective breeding for desired traits reduces the alleles within the
population, reducing the genetic diversity

Other species may be excluded by removal, culling or use of
pesticides

This leads to many individuals of the same species = low species
diversity