12. Human impacts biodiversity

What is biodiversity?

ndication of the number of different species in a habitat & how evenly balanced

the numbers of individuals are across the species

Agricultural practices that reduce Biodiversity (4)

1. Increased use of monoculture

2. Nutrient enrichment of soils

3. And loss of hedgerow (and woodland)

4. Increased use of pesticides

What is monoculture?

One crop being grown in a field / large area of farmland

What are the disadvantages of monoculture?

• Reduces biodiversity

• Increase in pest population specific to the crop

• Reduction of particular mineral content in soil (specific to needs of the crop)

‘Why is nutrient enrichment of soils used

To maximize crop yield / growth

(nitrate = aa & protein, phosphate = ATP, nucleic acids)

Why is the use of artificial fertiliser harmful?

Extra nitrate stimulates fast growth of a crop in comparison to other plants

(outcompetes them) = less biodiversity,

What else is nutrient enrichment used for and what are the other disadvantages?

Maintain high stocking rates (lots of grass to feed higher numbers of livestock)

Loss of soil crumb texture (soil particles less varied in size which reduces air spaces in soil) & makes erosion of fine soil particles easier

What are disadvantages to Loss of hedgerow (and woodland)

• Reduces biodiversity (less habitats & food for many species)

• Species at higher trophic levels In food chains lack food

Hedgerows act as wildlife corridors. What are these and why are they so important?

Areas linking woodland areas or habitats that are species rich

Allow movement & dispersal of species

Why might removal of hedgerows take place?

Make more land available for agriculture (& use of larger machines in larger sized fields)

Greater soil erosion – lack of protection from wind & rain, less roots of trees / shrubs to help hold soil in ground by binding

What are pesticides?

Kill organisms of many species not just target pest

If soil organisms killed – less decomposition & aeration of soil possible

Natural predators of pest may be killed – lead to increased numbers of pests (pest resurgence) as a result

Herbicides – (kill weeds) – reduces biodiversity of non-crop plant species & less variety of food for animals = less animal biodiversity

Some pest species may become resistant to pesticide

Bioaccumulation of pesticide in food chain – animals at higher trophic levels eat other organisms containing pesticide that the levels in their bodies is now toxic

What is polyculture?

Growing a variety or range of crops at same time / over a period of time in an area

What are the advantages?

•  Greater range of habitats & sources of food

•  More complex food webs & biodiversity

• What is crop rotation and why is it beneficial?

Planting different crops in turn, in the same field over a period of years

• Conserve soil fertility (each species has own different nutrient

requirements)

• Improve soil fertility (legumes, like pea, clover – add nitrate to soil due presence of nitrogen fixing bacteria in their root nodules)

• Reduces build-up of pest populations for a specific crop

What are the advantages of using organic fertiliser? (farmyard manure)

• Promote soil fertility

• Preserve soil crumb texture (greater humus – organic content in manure) to hold soil together

• Slower release of nutrients into soil – less chance of run off & loss of nutrients when it rains & plants will absorb more nutrients over a longer timeframe)

 Promote soil fertility

 Preserve soil crumb texture (greater humus – organic content in manure)

to hold soil together

 Slower release of nutrients into soil – less chance of run off & loss of

 Promote soil fertility

 Preserve soil crumb texture (greater humus – organic content in manure)

to hold soil together

 Slower release of nutrients into soil – less chance of run off & loss of

nutrients when it rains & plants will absorb more nutrients over a longer

timeframe)

What are the disadvantages of using organic fertiliser?

• Bulky & difficult to store or spread evenly

• Variable nutrient content

3. Hedgerow conservation and maintenance. What are the advantages?

Supports / promotes greater biodiversity – especially if plant species in hedgerows have a range of heights / age so that greater number of habitats & food sources are provided for nesting birds & other animals

Biodiversity hedgerow trimming will further increase biodiversity through:

Biodiversity hedgerow trimming will further increase biodiversity through

• Allow hedgerow tress to mature at intervals along the hedges

• Trim hedges at intervals over 2-3 year cycle (shrubs can flower& produce berries which are food for birds in winter)

• Trim in late winter – avoid destruction of bird nests in spring & allow berries to grow for winter food

• Stagger trimming – will provide a range of hedge heights & widths – maintain wide range of habitats for different species of birds & light penetration for plant species under hedges

It is important to protect the young hedgerow trees/shrubs from grazing. How can this be achieved?

New hedge should have mixture of woody plant species – trees & shrubs – to provide a wide range of habitats & avoid monoculture of hedge (not just one species of tree)

Plant hedge between double fence – provides a boundary that grazing animals find hard to penetrate

When hedge matures fence can be removed

What type of pesticides are used in place of broad spectrum pesticides and why?

Narrow-spectrum pesticides – only target & affect pest species

How does crop rotation help prevent the build-up of large pest populations?

Pest species cannot complete their life cycle or breed each year to build up population numbers (their preferred plant species is absent for a number of years as crops are changed each year in the cycle)

An alternative to pesticide us is Biological control. What is biological control?

Deliberate introduction of a species that will target the pest species – it could be a predator which feeds on the pest / a parasite that may attack a particular stage in the Life cycle of the pest so it can’t survive / it could be a pathogen that causes a disease to kill off the pest

What are the advantages of biological control?

• No chemical damage that may cause ecological harm to the environment or no bioaccumulation in food chains

• Targets only pest species – reducing chances of other species being killed or have their numbers decreased

• unlikely that pests will develop resistance (which could happen if a chemical insecticide is used – which can lead to only enabling individuals with resistance to the insecticide to survive but they can multiply rapidly)

• unlikely for pest resurgence to occur

• if successful – saves money in the long term & requires only careful monitoring not intervention for the most part as it is self regulating

What are the limitations of biological control?

• not always successful

• pest numbers fall below the level that can cause economic harm but are still present

• predator may not adapt to the environment & not thrive in enough numbers to reduce pest population enough

What are predator strips and what effect do they have?

small areas of rough grass / meadow left undisturbed at field edges – encourage increase numbers of natural predators of the pest species

Outline the steps leading to organic pollution(isolated & specific event)

Organic material – sewage, slurry & silage effluent - pollutes waterways

Rich source of nutrients for saprophytic bacteria involved in decay /decomposition

Bacterial numbers rapidly increase – population explosion – of saprophytic bacteria that use up oxygen in water for aerobic respiration

What is Biological Oxygen Demand (BOD)?

BOD – biological oxygen demand - gives indication of water quality (measures how much oxygen in the water is being used by organisms present)

More bacteria = more aerobic respiration = higher BOD (opposite occurs if less bacteria) see grap

>pollution leads to less oxygen present in water due to high numbers of bacteria feeding on & decaying organic substances

Outline the steps leading to eutrophication

Gradual & long term nutrient enrichment of waterway

Sequence of events

Excess nitrates / phosphates taken up by algae that use it for protein formation & growth algae number s increase rapidly (algal bloom) – that cover the surface which prevents light penetrating through water - aquatic plants deeper down will not be able to photosynthesize (shading effect)

algae use up the excess ions

aquatic plants & algae die then decomposed by saprophytic / saprobiotic bacteria in water

bacteria respire & use up oxygen in water

aquatic animals (fish, invertebrates) die due to suffocation (can’t respire aerobically)

reduction in biodiversity in water

What is the difference between organic pollution and eutrophication?

organic = quick & one specific event, eutrophication = gradual & long term pollution

Reducing eutrophication of waterways. What strategies have been taken to reduce eutrophication?

test mineral ion content of soil prior to applying fertilizer (ensure correct amount & balance of nutrients)

application of fertilizer restricted to periods of crop growth (set closed periods when not allowed to apply = avoid excess application / nutrients that can leach)

if heavy rain forecast do not apply fertilizer

avoid applying fertilizer close to waterways (especially if sloping land)

proper storage for slurry & farm waste to avoid leaks

follow government guideline

Areas of Specific Interest (ASSI) Details

ecologically important areas with high conservation value managed in co-operation with land owners

 Special Areas of Conservation (SACs)

areas given special protective status

under EU habitats directive

to protect threatened habitats or the species they contain

Biodiversity Action plans

policies & activities (meetings, design of information leaflets about conservation initiatives in local area)

organised at local council level in NI

Department of Agriculture, Environment and Rural Affairs (DAERA) agri- environment schemes

provide financial & other support to farmers & landowners to help support biodiversity & conservation of rare habitats

Northern Ireland priority habitat and species lists

identification of priority habitats & species which are most important from conservation or biodiversity standpoint by DAERA (due to Wildlife Act)

DAERA must inform

changes due to global warming and climate change

1. increased combustion of fossil fuels = > CO2 released into the atmosphere

2. deforestation on large scale (for farming, industry or urbanization) = <photosynthesis (less CO2 removed)

What is the link between co2 and global warming

close positive correlation between increased CO2 levels & global temperature

Explain what the greenhouse effect is and how it causes global warming.

short wave solar (visible & UV light) radiation given off by the Sun

reaches Earth’s surface

radiated back as longer wave heat radiation

some radiate out into space

some is absorbed by gases in atmosphere (CO2, methane, nitrous oxide) & trapped by this greenhouse layer (this ability has increased over a number of years)

then reflected back towards Earth & kept within Earth’s atmosphere

this leads to atmospheric temperatures increasing

Global warming on Melting of ice caps

raises sea levels

increased risk of flooding in coastal areas

polar ice thickness has reduced over time

extra water in oceans can disrupt ocean currents

Global warming on climate change

summers are getting warmer & wetter

What are the effects of global warming and climate change on ecosystems?

distribution of plant & animal species changes as temperature changes

loss of species typically found in northern regions

introduction of some species that not normally found in UK

increased desertification in warm areas

increased flooding

food chains affected by loss of species that are food for higher trophic levels

more rapid spread of disease in warmer conditions

one in ten species may be in danger of extinction in next few decades as their habitats are removed or changed