12 Enviro Science Revision - U3 Biodiversity

​Biodiversity refers to the variety of life on Earth, including species, genetic, and ecosystem diversity.

Biodiversity is essential for ecosystem resilience, allowing ecosystems to recover from disturbances like natural disasters and human impacts. It also supports ecosystem services such as food production, water purification, and climate regulation.

Levels of Biodiversity:

• Species diversity: Variety of species in an ecosystem.

• Genetic diversity: Variation within species’ genes.

• Ecosystem diversity: Variety of ecosystems in a region.

​Definition

• Variety of genetic traits within a population of a species.

• It allows species to adapt to changes in the environment by providing a pool of traits that might confer survival advantages under new conditions.

​Importance

• Survival of populations experiencing environmental changes such as climate change, habitat destruction, or the introduction of new diseases.

• Populations more likely to contain individuals with traits that allow them to survive, reproduce, and pass on advantageous traits to future generations.

Examples

• Climate Change: A population with diverse genetic traits is more likely to adapt to rising temperatures, altered precipitation patterns, or changing food sources.

• Disease Resistance: Populations with a wide range of immune system genes are more likely to survive disease outbreaks.

Solution

Species diversity refers to the variety of species within an ecosystem, while genetic diversity refers to the variation of genes within a species. Genetic diversity helps populations adapt to changing environments.

​Solution

Genetic diversity allows populations to adapt to environmental changes. If a population has a wide range of genetic traits, individuals with traits that are better suited to new conditions are more likely to survive and reproduce, ensuring the species’ survival.

​Provisioning services

Ecosystems provide goods that humans use directly.

• Potable water

• Food

• Fuel

• Fibre

• Pharmaceuticals

​Regulating services

Direct processes that control or moderate natural conditions to support human health and environmental stability. These services actively regulate or manage the environment.

• Control of climate

• Control of disease

• Pollination:

• Water purification

​Supporting services

Foundational processes that support life on Earth and maintain the conditions necessary for the operation of ecosystems. These services enable or support other services but don’t directly benefit humans in the immediate short term.

• Cycling of nutrients: Recycling elements like nitrogen and carbon to keep ecosystems functioning.

• Soil formation: Creating fertile soil that supports plant life.

• Photosynthesis: Plants converting sunlight into energy, producing oxygen for other organisms.

​Cultural services

Non-material benefits that contribute to human well-being:

• Aesthetic values: The beauty of nature, which inspires art and provides enjoyment.

• Recreational benefits: Ecosystems offer opportunities for leisure activities like hiking and fishing.

• Sense of place: The emotional and cultural connection people feel to a particular natural environment.

​Solution

Provisioning services provide direct goods such as food, water, fuel, and fibre that humans use. Regulating services control environmental processes like climate, disease control, and water purification, which indirectly support human health and well-being.

​Biodiversity through geological time

• Biodiversity has evolved over millions of years.

• Mass extinction events and climate shifts leading to periods of rapid species loss and diversification.

• Major extinction events, such as the one that wiped out the dinosaurs, drastically altered species diversity.

6 Mass Extinctions

• Ordovician-Silurian Extinction (approx. 444 million years ago):
  Caused by a severe ice age that lowered sea levels, wiping out many marine species.

• Late Devonian Extinction (approx. 375-360 million years ago):
  Affected primarily marine life due to climate change, ocean anoxia (lack of oxygen), and possibly asteroid impacts.

6 Mass Extinctions

• Permian-Triassic Extinction (approx. 252 million years ago):
  Known as the "Great Dying," this was the most severe extinction, with up to 96% of marine species and 70% of terrestrial species going extinct, likely caused by volcanic activity, climate change, and ocean acidification.

• Triassic-Jurassic Extinction (approx. 201 million years ago):
  Likely triggered by volcanic activity and climate change, this extinction cleared the way for the dominance of dinosaurs.

6 Mass Extinctions

• Cretaceous-Paleogene Extinction (approx. 66 million years ago):
  Most famous for wiping out the dinosaurs, likely caused by a large asteroid impact and volcanic eruptions, leading to global cooling.

• Current Extinction Crisis (6th mass extinction):
  Many scientists believe we are currently experiencing a sixth mass extinction, driven by human activities such as habitat destruction, climate change, pollution, and overexploitation.

​Solution

The "sixth mass extinction" is primarily driven by human activities such as habitat destruction, climate change, pollution, overfishing, and poaching. These factors are causing a rapid decline in biodiversity across the planet.

• Collection of all known fossils and their placement in the Earth’s rock layers.

• Provides evidence of the existence of species that lived in the past, their evolution, and the environmental conditions they lived in.

Natural changes over varying time scales can have significant impacts on ecosystem diversity, species endemism, the formation of diversity hotspots, and extinction rates.

- Volcanic eruptions, fires, El Nino, tectonic plate movement, evolution

​Endemism

Some species evolve in isolation due to geographical barriers like mountain ranges or oceans, becoming endemic to specific regions. Australia, for instance, has a high number of endemic species, including kangaroos and koalas.

​Solution

When tectonic plates shift, they can isolate populations of species, preventing them from interbreeding with other populations. Over time, these isolated populations evolve separately, leading to the development of species that are only found in specific regions, known as endemic species.

​Habitat loss & Over-exploitation

• Human activities such as deforestation, urbanization, and agriculture

• Isolate small populations by destroying habitats.

• Over-exploitation (e.g., overfishing, poaching) reduces population sizes, increasing the risk of extinction.

​Inbreeding Due to Small Population Size

• Small, isolated populations

• Leads to reduced genetic diversity and increased susceptibility to diseases and environmental changes.

Loss of Pollinators, Dispersal Agents, and Symbionts:

• Species depend on relationships with:

  • pollinators (e.g., bees)

  • dispersal agents (e.g., birds)

  • symbionts (e.g., fungi) for reproduction and survival.

• Bioaccumulation: Certain pollutants (e.g., mercury, pesticides) accumulate in the tissues of organisms.

• Biomagnification: These pollutants become more concentrated as they move up the food chain, affecting top predators like eagles and large fish.

Climate Change

Rising temperatures, changing weather patterns, and sea level rise alter habitats and force species to migrate, often leading to loss of biodiversity.

Disease & Introduced Species

• Both human-induced (e.g., wildlife trade) and naturally occurring diseases can decimate species populations.

• Non-native species introduced by humans often outcompete native species for shelter, food, and water, disrupting ecosystems and causing declines in native biodiversity.

Solution

Overexploitation reduces the population of species to a level where they cannot recover. This can lead to a decline in genetic diversity, disrupting ecosystems and pushing species toward extinction.

​Translocation

Moving species from one location to another to reduce threats or restore populations. For example, translocation of Bilbies to predator-free reserves in Australia.

Re-introduction

Returning species to areas where they have been locally extinct. This is often done through captive breeding programs. An example is the re-introduction of the Tasmanian Devil to mainland Australia.

Captive-breeding programs

Breeding endangered species in captivity to increase population numbers and eventually reintroduce them into the wild. While beneficial, captive breeding can sometimes lead to challenges when animals struggle to adapt to the wild.

AND

• Protected areas

• Retaining remnant (left-over) vegetation

• Wildlife corridors/zones

• Gene banks

• Reduction & improved targeting of pesticides in ag/urban areas

Solution

Advantage: Re-introduction helps restore ecosystems by returning species to their natural habitats.

Disadvantage: Reintroduced species may struggle to survive if their habitat has changed or if they lack survival skills due to captivity.

Solution

Translocation involves moving species from a threatened or degraded habitat to a safer, more suitable location. This helps conserve species by giving them a chance to thrive in environments that are better suited to their survival. Translocation may be necessary when a habitat is being destroyed by human activities, such as urbanization or deforestation.

Options for renewing/regenerating

• Restoration of habitat

• Erosion control

• Reintroduction of previously endemic species

Grids

• Grids divide an area into equal sections

• Species are sampled in each section.

• This method helps estimate species abundance and distribution across large areas.

​Transects

• A straight line laid across a habitat.

• Species are sampled at regular intervals along the line

• Study how species composition changes across environmental gradients (e.g., moisture, light).
  

​Edge Effects

• Occur where different ecosystems meet (e.g., forest meets grassland).

• Species diversity and density may be higher or lower at these boundaries, and transects help assess these changes.
  

Random vs Systematic

Random sampling is used to eliminate bias, while systematic sampling is used to understand species distribution across a gradient, such as from a riverbank to the forest edge.

​Quadrats

• Quadrats are square, rectangular, or circular plots used to sample species in a defined area.

• The shape can affect the accuracy of the sample, with square or circular quadrats commonly used to reduce edge effects.

​Quadrats

• Edge effects in quadrats occur when the species at the boundary of a quadrat are not truly representative of the whole area.

• Larger or multiple quadrats reduce the impact of edge effects.

Solution

A transect is a line laid across different environmental zones, such as a beach or a forest edge. Samples are taken at set intervals along the transect, allowing researchers to observe how species composition changes along the environmental gradient.

​Solution

Edge effects occur at the boundary between two ecosystems, where species composition may be higher or lower than in the core areas. This can lead to an overestimation or underestimation of species diversity in transect studies.

​Mark and Recapture Method

• Used to estimate the population size of mobile species.

• A sample of individuals is captured, marked, and released.

• After a set period, another sample is captured, and the number of marked individuals is recorded.

​Calculating population size

Population size is estimated using the formula:
N= (M x C) / R

Where:

• N = estimated population size

• M = number of individuals marked in the first sample

• C = total number of individuals caught in the second sample

• R = number of marked individuals recaptured

Species Richness

• Refers to the total number of different species present in a given area. It is a simple count of species, regardless of their abundance.

Simpson's index of diversity (SID) (0-1)

• A measure of species diversity that accounts for both species richness and species evenness (the relative abundance of each species). It gives more weight to species that are more abundant.

The International Union for Conservation of Nature (IUCN) Red List categorizes species into the following ranks:

• Extinct in the Wild: only survive in captivity or outside their natural habitat but are no longer found in the wild.

• Critically Endangered: extremely high risk of extinction in the immediate future. Population numbers are critically low, and urgent conservation measures are needed.

• Endangered: very high risk of extinction in the near future. Population numbers are rapidly decreasing, and their habitat is severely threatened.

• Vulnerable: high risk of extinction in the medium term. They have decreasing populations but are not yet at immediate risk.

• Near Threatened: close to qualifying as vulnerable but are not currently at high risk of extinction.

• Least Concern: widespread and abundant, with no immediate threat to their populations.

Solution

Critically endangered species face an extremely high risk of extinction in the immediate future and require urgent conservation actions. Endangered species are at a very high risk of extinction but may have slightly higher population numbers or more stable habitats compared to critically endangered species.

• Availability of suitable habitat

• Geographic distribution

• Population size

​Solution

Species with a restricted or shrinking geographic distribution are more vulnerable to habitat loss and environmental changes. If the species is confined to a small area, a natural disaster or human activity can lead to the complete loss of their habitat, increasing their risk of extinction.

A range of legal treaties, agreements, and regulatory frameworks are in place to protect threatened species at various levels:

International

• Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES):
  An international agreement that regulates trade in endangered species to prevent over-exploitation.

• IUCN Red List of Threatened Species:
  A global inventory assessing the conservation status of species to inform global conservation priorities.

National

• Environment Protection and Biodiversity Conservation Act 1999 (Cth):

  (EPBC Act)
  The primary national environmental law in Australia, protecting biodiversity and managing impacts on nationally significant species and ecosystems.

State

• Flora and Fauna Guarantee Act 1988 (Vic):

  
  A key state law aimed at protecting endangered species and ensuring the conservation of Victoria’s biodiversity.

Local

• Classified World Heritage Areas:
  Areas protected due to their cultural, historical, and environmental significance, such as the Great Barrier Reef.

• Local Government Conservation Covenants:
  Legal agreements that protect habitats on private land, ensuring long-term conservation efforts at the local level.

​Solution

CITES regulates the international trade of endangered species by ensuring that listed species are not exploited commercially. It prevents over-exploitation and helps species recover by limiting exports and imports.