A4.2 - Conservation and biodiversity

A4.2.1 Biodiversity as the variety of life in all its forms, levels and combinations

Biodiversity is the variety of life existing on multiple levels

  • Ecosystem diversity is the range of different habitats or number of ecological niches per unit in an ecosystem (e.g. woodland may have high diversity, desert has low)

  • Genetic diversity is the range of genetic material in a gene pool or population of a species. A large gene pool leads to a high genetic diversity

  • Species diversity is the variety of species per unit area. This includes both the number of species present and their relative abundance

    • Species diversity can be determined by estimating the richness and evenness of species in an area

    • Richness refers to the number of a species in an area (more species = greater richness), and evenness to the relative abundance of each species (similar abundance = more evenness)

Calculating the Simpson’s reciprocal index can be used to describe and compare communities and their diversity. Their values can help to understand the impact of human development on ecosystems.

  • D = N(𝑁 − 1)/Σ𝑛(𝑛 − 1)

  • N is the total number of individuals of all species, Σ𝑛 is the number of individuals of each species and D is diversity

  • Sessile species numbers and abundances can be sampled by random qudrat sampling in an area of interest and their values inserted into the formula shown above

  • Low diversity could indicate pollution, eutrophication, recent colonization of a site or agricultural management

Biodiversity levels are difficult to estimate and even more so when looking into the past

  • Relative levels can be deduced from fossil evidence

  • There have been five mass extinctions, with the last one having occurred 66 million years ago. Since then, the biodiversity is steadily increasing

A4.2.2 Comparisons between current number of species on Earth and past levels of biodiversity

The level of biodiversity on Earth is not a constant and instead is always fluctuating

  • New species can arise over time as a consequence of evolutionary change leading to eventual speciation (formation of new and distinct species in the course of evolution)

  • Species numbers may also be diminished when external factors result in the complete eradication of a species (extinction)

  • Evidence from fossils suggest that there may be currently more species alive on Earth today than at any time in the remote past

    • Currently, there are roughly 1.2 million species that have been recorded and classified, but estimates suggest there could be a further 7.5 million species yet to be discovered

  • The accuracy of a species diversity estimate is dependent on the mechanisms used to determine species classification

A4.2.3 Causes of anthropogenic species extinction

  • Global climate change

  • Overharvesting

  • Pollution

  • Invasive species

  • Habitat destruction

The north island giant moas

  • Were a group of flightless birds, native to New Zealand

  • They grew up to 3.6m tall and had a mass of approximately 230kg

  • New Zealand was not settled by humans until the arrival of Polynesians in the 13th century, who became the Maori

  • It took less than 200 years for all species of moa to be hunted to extinction (overhunting and habitat destruction)

The Caribbean monk seal

  • The only seal species native to Central America

  • Declared extinct in 2008, with the last confirmed sighting in 1952

  • This species had a broad range throughout the gulf of Mexico

  • They were widely hunted for their blubber, for oil and for their meat

  • Overfishing of their food source led to starvation

  • They were know as nonaggressive as well as sensitive to disturbance, factors that humans exploited until they were extinct

A4.2.4 Causes of ecosystem loss

An ecosystem consists of the interactions between all living organisms (a community) and their abiotic environment (habitat). Ecosystems can become threatened by direct human activities (e.g. deforestation) or indirectly (e.g. climate change).

  • Land use change for agricultural expansion

  • Urbanisation

  • Overexploitation of natural resources

  • Mining and smelting industry

  • Leaching of fertilisers

  • Climate change

  • Building dams

  • Drainage or diversion of water

The Aral sea

  • Between Kazakhstan and Uzbekistan

  • Was the fourth largest lake in the world, fed by rivers and without outflows

  • Ecosystem diversity was big

  • Causes of the loss of this ecosystem are the increase in global temperatures, which lead to the reduction of water area and depth by evaporation

  • This further lead to an increase in salinity and consequentially, ecosystem collapse

Dipterocarps

  • A family of trees that function as a keystone species within the rainforest ecosystems of South Asia

  • Their presence provides an important habitat for native species in addition to providing nutritional support via fruits, pollen and nectar

  • These forests are progressively being lost in order to provide timber and clear the land for agriculture (e.g. palm oil plantations)

  • In Borneo, excessive deforestation is endangering native species like the orangutan, as well as threatening the water security and food sovereignty of the indigenous populations

Great barrier reef

  • Coral species form connected reefs that are greatly impacted by changes in oceanic temperature or pH

  • Coral polyps receive nutrition from photosynthetic zooxanthellae (algae) that live within the polyp’s endodermis

  • Changes in ocean temperature or pH may cause zooxanthellae to leave the coral tissue, leading to coral bleaching

  • Anthropogenic greenhouse gas emissions are increasing oceanic temperatures and decreasing pH (ocean acidification)

  • This has resulted in mass bleaching of the Great barrier reef off the coast of Australia, threatening the indigenous marine ecosystem

A4.2.5 Evidence of biodiversity crisis

Sources of evidence for the biodiversity crisis are government sites which gather and collect evidence by monitoring.

  • The state of biodiversity is assessed and reports are periodically produced

  • Swissre is a company which does that

There are many ways to gather evidence

  • Determining population size in an area over years

  • Range of species in an area

  • Diversity of a species in an ecosystem

  • Richness and evenness of biodiversity in an ecosystem (Simpson diversity index)

  • Extent of degradation of an ecosystem

  • Number of threatened species within a taxonomic group

Ecosystem stability requires a high level of both species richness and species evenness in order to resist environmental change

  • An ecosystem with many species but few individuals within each population would not be stable (low evenness)

  • An ecosystem with only a few species consisting of many individuals would similarly lack resilience (low richness)

A4.2.6 Causes of current biodiversity crisis

Although biodiversity has never been as high as it is now, mostly due to the absence of another mass extinction in the last 66 million years - a widespread ecosystem collapse has unfolded over hundreds of thousands of years.

  • The current sixth mass extinction is happening much more rapidly due to…

    • Hunting and overexploitation

      • Excessive or unnecessary hunting may reduce population numbers below sustainable levels

    • Urbanisation and land loss

      • Human construction can lead to a direct loss or a fragmentation of habitats, resulting in increased competition between native species

    • Deforestation and land clearance

      • The clearing of land for industry or agriculture results in a consequent loss of native habitat

    • Pollution of land and sea

      • Microplastics, along with fertilisers and organic waste products, can cause ongoing damage to natural environments

    • Spread of invasive species

      • Global transport/globalisation is increasing the spread of pests, pathogens (infectious diseases) and invasive species

    • Climate change

      • Greenhouse gases released via industrial processes are changing climate conditions and increasing ocean acidification

  • All of these causes aren’t new, but have intensified over the last 100 years, explaining the increase in impact

  • The reasons for the rise in these activities is largely due to overpopulation

    • Since 1920 the population size has increase from 2 billion people to almost 8 billion

    • This crisis is said to be anthropogenic as the causes are a consequence (direct or indirect) of human activity

A4.2.7 Need for several approaches to conservation of biodiversity

The biodiversity crisis is acute and often multiple strategies are required to reverse or maintain ecosystems

  • Biodiversity conservation can be…

    • In-situ conservation

      • National parks

        • The Swiss national park is a strictly protected wilderness where flora and fauna can develop freely, and natural processes are allowed to run their course unhindered

        • Founded in 1914, it is the oldest national park in the Alp and at the same time the only wilderness area with the highest conservation status

      • Biosphere reserves

        • Terrestrial

        • Marine

      • Nature parks or wildlife sanctuaries

    • Ex-situ conservation

      • Seed banks, cryopreservation, field gene banks

        • Switzerlands Agroscope Gene Bank is over a century old, and the varieties collected 120 years ago are still preserved and available

        • Regular exchanges take place with other banks and research centres as a part of variety selection programmes

      • Botanical gardens, arborata, zoos (captive breeding), aquariums

        • In Switzerland, some 3000 species and varieties of trees and shrubs, mainly from the worlds temperate regions, are to be found at the national Arboretum in the valley of the Aubonne river

        • The Botanical garden Basel contributes to the ex-situ conservation of endangered plant species from in and outside of Europe. It also hosts a collection of old trees estimated at an age of ca. 130 – 150 years.

        • The Zoological garden Basel is actively involved in over 40 ex-situ programmes and captivation breeding programmes for endangered species

      • Home gardens, sacred plants

Compare and contrast in-situ and ex-situ conservation

  • In-situ

    • Description

      • Preservation of species within their natural environment/habitat

      • This typically involves the designation of protected areas of land as either nature reserves or national parks

    • Advantages

      • Keeps organism within natural food chains/webs

      • Allows organism to stay where they are adapted to

      • Maintains normal behaviors

      • The goal is to maintain and preserve entire ecosystems/areas

    • Disadvantages

      • Sometimes might not be efficient

      • Might lead to decrease in genetic diversity (control of emigration)

      • Greater maintenance and costs involved

  • Ex-situ

    • Description

      • Preservation of plants and animals outside their natural habitats

      • It usually involves critically endangered species when urgent intervention is required

    • Advantages

      • Greater control of conditions

      • Less competition and stress for food etc. in a limited space

      • Continuation of species that have lost their habitat permanently

    • Disadvantages

      • Doesn’t help to prevent the destruction of the environment

      • Limited genetic diversity because species are within a shallow gene pool

      • Species raised in captivity are less likely to be re-introduced back into the environment

A4.2.8 Selection of evolutionarily distinct and globally endangered species for EDGE

The EDGE of existence programme is a global conservation initiative that uses a scientific framework to select species for conservation prioritisation.

  • A species must be Evolutionary Distinct and Globally Endangered (EDGE) to be selected for prioritisation

    • Evolutionary distinct species have few close relative and represent unique phylogenetic branches

    • Globally endangered species may be defined as at risk according to the IUCN red list for threatened species

  • The EDGE programme is used to inform relevant stakeholders of conservation priorities - it does not make decisions regarding interventions

    • Keystone species may not be globally endangered, but they may require greater priority for conservation due to their integral role within an ecosystem

    • Certain species may be considered culturally significant and hence be prioritised according to political need