AQA A Level Biology复习笔记4.6.4 Conservation & Farming

• After the second world war there was a massive change in how food was produced
• There was a need to produce more food, at a quicker rate
  • In other words farmers needed to produce a higher yield

   

• It was then that modern farming practices began:
  • Farms became more specialised so they grew only one crop or raised one type of livestock (monoculture)
  • There was a switch to growing cereal crops rather than vegetables
  • Fields were made bigger to accommodate machinery via the removal of hedgerows and stonewalls
  • More land was made arable by draining wetland and filling in ponds
  • The use of pesticides and fertilizers massively increased

   

Effects of Modern Farming on Biodiversity

• Biodiversity looks at the range and variety of genes, species and habitats within a particular region
• In relation to farming the biodiversity of insect, animal and plant species is often measured and studied
• Some modern farming techniques have had a major negative impact on the level of biodiversity present in farming areas
• Conservationists have made strong efforts to try and maintain or improve biodiversity around farmlands
  • They have rewilded areas by removing all human interference and reintroducing native species
  • Organic farming has been largely promoted and encouraged

   

Improving grazing land

• Nutritious, fast-growing grass is essential for raising healthy livestock
  • A dairy cow is capable of eating almost 20kg of dry biomass in one day

   

• A mixture of ryegrass and white clover species provides the highest quality grazing pasture. This species only grow on drained, fertilised land
• Farmers deliberately fertilise and drain the land and sow the seeds of these two plant species
• As a result, other plant species are either outcompeted or the changes to the land mean it is no longer a suitable habitat for them - there is low species richness
• Natural grazing land that hasn’t been interfered with has a large variety of plant species present which can support a much greater range and number of insect species and bird species
• Wet grasslands have declined steeply in the last 100 years and are now regarded as biodiversity hotspots

Sowing of cereal crops

• For farmland bird species the ploughing of fields and the harvesting of crops are the two points in the year when food is plentiful
  • Ploughing brings invertebrates to the surface
  • Harvesting provides spilt grain from the crops and seeds from weeds, as well as making invertebrates more accessible by removing their cover

   

• Traditionally crops were sowed in the spring
  • The soil was ploughed in March
  • Grains were sown in late April
  • Harvest took place in September
  • The gap between harvesting and ploughing was significant - five or six months

   

• Modern farming has switched to sowing crops in the autumn
  • The soil is ploughed in August
  • Grains are sown in September
  • Harvest takes place in July
  • The gap between harvesting and ploughing is very short - one or two weeks

   

• The smaller gap between harvesting and ploughing means there is a very short period of time during the year when food is plentiful for birds however there is less time where the soil is redundant for the farmer
• Scientists believe that this switch from autumn to spring sowing will greatly reduce the diversity of farmland birds in the future

Organic farming

• Many people favour the produce from organic farms as the food produced is free from harmful chemicals
  • The use of pesticides and inorganic fertilizers is highly restricted on organic farms

   

• The reduction in the use of these chemicals is also thought to benefit biodiversity in and around organic farms
• This is a common viewpoint however there is currently very little scientific evidence that backs these claims

The decline of the bumblebee

• Bumblebee are essential pollinators that pollinate wildflowers and valued crops such as oilseed rape and peas
• Almost a quarter of the European bumblebee species are threatened with extinction
• There has been a very rapid decline in bumblebee numbers in recent years
• Bumblebees require habitats with a large number of flowering plants to ensure a supply of pollen and nectar all year round. Examples of this are hedgerows, field margins and grasslands
• It has been suggested that the extensive farming of crops and the use of pesticides are contributing to this decline
  • The monoculture of crops reduces plant diversity for bumblebee habitats
  • Although they are not the target species, pesticides can have a negative effect on bumblebees

   

• There is still inconclusive evidence as to whether these modern farming methods are the cause of the bee’s falling numbers

Biodiversity vs Profit

• A high yield and profit are two factors that make farming economically viable
• Farming practices that maintain or increase biodiversity can be expensive, labour intensive, time-intensive. They can also reduce the yield of crops and livestock
  • For example, if a farmer stops using pesticides on crops, the number of bumblebees will increase but the number of pest species that destroy crops will also increase which will reduce crop yield and profit
  • This means that the farmer will have to charge more for his produce, in what is a very competitive market

   

• It is difficult to find the balance between conservation and farming due to these knock-on effects
• The EU has several grant schemes set up to encourage farmers to use more environmentally friendly farming techniques. The money provided by the grants can offset any profit lost due to lower yield