Threats to biodiversity: Changes in abiotic and biotic factors

What is an abiotic factor and some examples?

Non-living

• Soil pH, water, sunlight, wind, gas, minerals, humidity, temperature

What is a biotic factor and some examples?

Living

• Plants, animals, bacteria, fungi

Changes in abiotic factors

Human activities may alter a habitat so it becomes unstable for species not adapted to new conditions. Species with specialised habitat requirements are most likely to be effected by the changes.

• Human activities

• Temperature

• Dissolved oxygen

• PH

• Water turbidity

• Physical damage

AF- water availability

Human activities:

• Land drainage and over exploitation of groundwater resources lowers the table

• HEP stations may cause sudden changes in water levels

Consequence:

• Surface habitat wetlands dry out, making it impossible for wetland species sp survive

• Flooding- can’t swim

• Species with long tap roots may do better than those without it

AF- temperature

Human activities:

• Hot effluent water can increase growth of aquatic plants

• GCC

Consequences:

• Growth and survival of some species increase but others may suffer if not adapted

• GCC- species recolonise other areas

AF- dissolved oxygen

Human activities:

• Levels reduce when discharging hot water from power stations

• Levels also reduce when discharging organic wastes, this deoxygenates the water as it decomposes

Consequences:

• Aquatic aerobic organisms may die, reducing biodiversity, e.g. insect larvae, fish

AF- pH

Human activities:

• Mine drainage water and pollutant gases from burning fossil fuels, or smelting metals produce acidic conditions (acid rain)

Consequences:

• Denature cell proteins of exposed tissues

• Fish eggs, fish gills and calcium based exoskeletons are susceptible

• Tree death

• Root cell enzymes may not function and they become unable to absorb nutrients

• Many plants can only survive if the soil is within a particular pH range

AF- water turbidity

Human activities:

• Ploughing, mining or dredging may increase water turbidity

Consequences:

• Reduces light penetration so prevents aquatic plants from photosynthesising, reducing oxygen

• Kills filter feeding organisms

AF- physical damage

Human activities:

• Ghost fishing (discarding old gear)

• Discarding litter

Consequences:

• Sea animals caught in nets (get stuck/ can’t swim) So drown

• Animals stomachs fill with plastic so they can’t eat food, causing them to die of starvation

Changes in biotic factors

Survival of a species may be affected by changes in the presence and abundance of other species in its habitat

• Pollinators

• Seed dispersal species

• Food chain impacts

BF- pollinators

Human activities:

• Habitat loss and pesticides

Consequences:

• Plants rely on insects to transport pollen between flowers

• Without pollinators, these plants can’t reproduce

BF- seed dispersal species

Human activities:

• Habitat loss and hunting reduce species population

Consequences:

• Vital in successful dispersal of seeds and therefore future plant survival

• Decline in dispersal has led to a decline in many tropical plant species

BF- food chain impacts

Human activities:

• Hunting

• Habitat change and loss

Consequences:

• Some species have declined as their food source has been over exploited by humans

• This has led to a decline in species from further up the chain as their food source has declined