Environmental Science - Chapter 4

Human Influences that pressures and affects Biodiversity

• Land Clearing

• Urbanization

• Over-Exploitation

• Climate Change

• Pollution

• Introduced Species

Non Human Influences that pressures and affects Biodiversity

• Volcanic Eruptions

• Earthquake

• Floods

• Fires

• Cyclones

• Disease

Habitat Modification

Refers to changes that are made to an environment that affects the living conditions of organisms.

How can Volcanic Eruption affect environments

• Destroys habitats that organisms live in due to reducing producers.

• Improves soil quality, leading to an increase in biodiversity.

• Lead to plant species becoming dominant within an environment.

How can Earthquakes affect environments

• Separate populations, leading to fragmented populations due to the formation of mountains of valleys.

• Landlines can occur due to burying plants and animals underneath.

• Trees can fall due to forest structure as ground plants are exposed to more light allowing them to grow.

How can Fires affect environments

• Can reduce overall biodiversity as many plants and animals die in the fire

• This means predators searching for prey after a fire will find it difficult to find food and herbivores will have limited opportunities to find food.

• After a fire the soil contains high levels of nutrients which allow for new plant species to grow, which attracts animals, these animals attract other animals changing the ecosystem

• Trees and hollows are removed from the environment as they get wiped out by the fire meaning animals who rely on these hollows move to a different environment.

• Increased erosion as without vegetation, rain and wind can wash away soil, leading to desertification.

How can land clearing affect environments

• Large areas of forests, grasslands, and wetlands are cleared for crops and livestock farming.

• The loss of trees reduces habitat for birds, insects, and mammals that depend on forests for food and shelter.

• Death of fish lead to collapses in food chains and webs.

• Native plant species decline, and ecosystems become less diverse. Organisms leave the environment which leads to a cascade effect where other organisms follow as many interactions that occurred in that environment can no longer be sustained.

• Some agricultural crops become invasive, spreading beyond farmland and outcompeting native species.

Urbanization

Clearing for natural habitats for the expansion of cities and human settlement.

Urbanization Affects on ecosystem

• Splits natural habitats into smaller, isolated patches.

• Vehicle emissions and industrial activities contribute to air pollution, harming plants and animals.

• Light and Noise pollution interferes with animal behaviour, affecting bird migration, nocturnal species, and insect populations.

Habitat Fragmentation

Refers to the process where a large, continuous habitat is divided into smaller isolated fragmentation due to development of roads, farms, factories, fences and industries.

Effects of Habitat Fragmentation

• These processes form barriers between the remaining isolated areas of suitable habitats.

• The once large population of species are reduced to several smaller populations which are more susceptible to changes to their environment and increases their risk of inbreeding and outbreak of disease.

• Reduces gene flow between populations leading to lower genetic diversity

• Species diversity is also reduced as smaller habitats can support a reduced number of species.

Habitat Edge effect

• The edges of a habitat are more susceptible to impacts from the surrounding areas.

• The edges of the fragmented habitats are more prone to interactions such as human animal interactions.

• Edges of ecosystems also have slightly different conditions such as light exposure, wind exposure and temperature variations.

• Species interaction can also occur within these edges with additional competition, predation and invasion by non native species.

• Narrow habitats are more affected by the edge effect as these environments have a higher ratio of edge areas to core areas.

• Circular habitats have the lowest ratio of edge areas and provides the best protection to biodiversity.

Overexploitation

When natural resources are used at a rate faster than ecosystems can regenerate.

What goes under Over Exploitation

• Deforestation: Deforestation becomes more faster and increased due to being more efficient at cutting trees, due to improved technologies.

• Over hunting: With more equipment such as sonars, ships, resulted in fishes being caught more.

• Over Grazing: Excessive gazing removes vegetation, leading to soil erosion and desertification.

• Overhunting and Poaching: Hunting for food, trophies and illegal wildfire trade leads to species declines and extinction.

How are Small Populations created?

• Fragmentation

• Habitat Loss

• Habitat Modification

Loss of Pollinators, Dispersal Agents, Host Species and Symbionts

• Reduction in biodiversity can lead to the removal of certain species that are critical for the survival of other organisms.

• This includes pollinators which are important in plant reproduction and provide a regulating service to the environment, if pollinators are removed from the ecosystem then this reduces the overall producer population reducing the amount of food available.

• Plants are also important in maintaining the water cycle as they absorb water from the atmosphere and bring water back into the atmosphere via transpiration.

• The lack of food means that certain species will not be attracted to the habitat and will not occupy the space.

• Many organisms also act as dispersal agents where they may ingest or have seeds attached to their fur dispersing them within the environment. If the habitat is not suitable for their survival these processes cannot occur.

How are small populations be affected by inbreeding

• Small populations can also suffer from inbreeding which is breeding between individuals that are closely genetically related.

• Closely related individuals further reduce the genetic diversity within the population. Inbreeding can lead to increases in levels of homozygosity passing on harmful alleles to offspring more easily.

• This can be seen when deleterious recessive alleles are passed onto the next generation and expressed as organisms receive two deleterious alleles from inbred parents.

• This can lead to a reduction in the populations overall fitness and lead to an inbreeding depression where the populations fitness declines due to high levels of inbreed.

• Inbreeding can also lead to reduced fertility and birth rates, reducing immune function making them more susceptible to disease, genetic disorders and mutations.

How are smaller populations affected by disease

• Disease can spread more rapidly in a small populations as individual are more likely to come onto contact with one another.

• Small populations are more susceptible to disease as many individuals are genetically similar so many of the members will lack enough genetic variation within them to combat the disease.

• It would also be less likely for an individual with different alleles that may provide some additional immunity to the disease as they would have low genetic diversity.

• Sometimes diseases can mutate and be past on from one species to another species.

• This can be seen when domesticated animal diseases can pass to native animals which do not have immunity against them as their body has not had previous exposure. Fragmented populations are more likely to be in contact with domestic animals increasing their chance to be exposed to disease.

Pollutants

Substances that are released into the ecosystem by human activity which decreases and degrades the quality of the ecosystem.

Origins of Pollutants

Can originate from nearby farms which release herbicides and pesticides, leaching into water ways and impacting the chain chains.

Bioaccumulation

The gradual accumulation of persistent, non biodegradable pollutants within an organism. And occurs when an organism absorbs a substance faster then it can remove.

Biomagnification

The increase in concentration of a pollutant in the tissue of organisms as they move higher up the food chain, and usually the predator ends up with the high levels of pollutants as they eat their prey that also absorbs pollutants.

Plants as Filters

They act as a supporting service within the ecosystem as they are ale to filter out pollutants and purify water.
It does this by:

• Slowing down flow of water, trapping material and break down pollutants, helping purify water.

• Pollutants become buried in sediment and are converted into less harmful chemical forms by biological processes.

• Nitrogen and phosphorus are absorbed by plants before they enter waterways and cause eutrophication.

• Plants are broken down and recycled/imbedded in the sediment. Harmful chemicals = gone.

Climate Change

Refers to the long term shift in temperature and weather patterns, and can be naturally occurring or caused by human activities.

Effects of Climate Change

• Increase in global temperatures.

• Frequency of extreme weather events such as droughts and floods.

• Rising sea levels.

• Increase in bush fires.

Tolerance Range

The range in which environmental conditions are tolerable for survival of species.
Whenever an organism is out of the range, they become stressed and may become extinct if the conditions outside are too much.

Biotic and Abiotic Factors included in tolerance range.

• Includes factors such as amount of food and shelter.

• And temperature and average weather conditions.

How can climate impact ecosystems?

• As the climate changes its average weather pattern and temperatures within the ecosystem, the organisms cannot adapt due to their low genetic diversity, risking the organisms to become extinct.

• It makes it harder for organisms to migrate to new locations.

• Cutting down forest will result in greenhouse gas emissions being even higher.

• Less producers = less biodiversity.

Photosynthesis

Enables plants to convert atmospheric carbon dioxide into sugars, and provides food and raw material to the survival of the ecosystem and humans.

Impacts of droughts on ecosystems

• Reduces the ability for producers to photosynthesis, and causes plants to dry out.

• Reduction in vegetation.

• Reducing food and shelter for organisms.

• Dehydration for organisms.

• Can disrupt symbiotic relationships with birds and plants or predator and prey.

• Increases the risk of fire → Genetic Bottlenecking events

Floods

Overflow of water that submerge land that is generally dry.

Impacts of Floods on ecosystems

• Habitat is destroyed → Forces organisms to move to new environments they are not adapted to survive in.

• Spread disease by flood water.

• Excessive moisture in soil → Decrease oxygen levels → Plants are unable to respire and therefore suffocate and die.

• Contributes to Biomagnification and Bioaccumulation by carrying pollutants through water.

Introduced Species

Exotic species that have been deliberately or accidently introduced into a new region.

Impacts of Introduced Species on ecosystems

• Compete with native organisms for resources such as food, shelter and water. → Makes it harder for native organisms to get food normally.

• Non-Native species act as predators, and eat native animals.

• Introduced Plants = Replacing and outcompeting native plants.

• Animals reliant on native plants will die.

• Introduced species uptake water from rain → Native Plants do not receive water limiting their growth.