chapter 11 p3 Flashcards
Climate change:
In 2007, the Intergovernmental Panel on Climate Change (IPCC) released a report summarising scientists’ current understanding of climate change.
The report took six years to produce and involved over 2500 scientific personnel in its production.
Some of the key findings include the following:
Some of the key findings include the following: p1
- The warming trend over the last 50 years (about 0.13°C per decade) is nearly twice that for the previous 100 years.
- The average amount of water vapour in the atmosphere has increased since the 1980s over land and ocean. The increase is broadly consistent with the extra water vapour that warmer air
- Since 1961, the average temperature of the global ocean down to depths of 3 km has increased.
The ocean has been absorbing more than 80% of the heat added to the climate system, causing seawater to expand and contributing to sea-level rise. - The global average sea level rose by an average of 1.8mm per year from 1961 to 2003. - There is high confidence that the rate of observed sea level rise increased from the 19th to the 20” century.
- Average Arctic temperatures have increased at almost twice the global average rate in the past 100 years.
- Mountain glaciers and snow cover have declined on average in both hemispheres.
Widespread decreases in glaciers and ice caps have contributed to sea-level rise. - Long-term upward trends in the amount of precipitation have been observed over many regions from 1900 to 2005.
climate change research p1
To enable our understanding of climate change to develop. significant quantities of data have been developed charting changes to the Earth’s climate over time.
This has required an enormous international co-operative effort over many years. It is only on the basis of reliable, irrefutable evidence that decisions of an international significance can take place.
Decisions made now may have far-reaching consequences for the populations of individual countries or continents today, as well as far-reaching global implications for the future.
climate change research p2
The need to produce reliable data for issues of this scale is paramount.
Despite the weight of evidence for climate change, some scientists still believe that a causal link between human activity and climate change is yet to be established.
Global warming refers to a rise in the Earth’s mean surface temperature.
The Earth’s climate has shown fluctuations in temperature throughout its history, so it is not possible to say for certain that humans are directly causing global warming.
However, carbon dioxide levels in the atmosphere have significantly increased since the industrial revolution, trapping more thermal energy in the atmosphere.
Therefore most scientists believe that human activities are contributing to global warming.
If global warming continues, biodiversity will be affected. For example: p1
The melting of the polar ice caps could lead to the extinction of the few plant and animal species living in these regions.
Some species of animals present in the Arctic are migrating further and further north to find favourable conditions as their habitat shrinks.
Increasing global temperatures would allow temperate plant and animal species to live further north than currently.
Rising sea levels from melting ice caps and the thermal expansion of oceans could flood low-lying land, reducing the available terrestrial habitats.
Saltwater would flow further up rivers, reducing the habitats of freshwater plants and animals living in the river and surrounding areas.
If global warming continues, biodiversity will be affected. For example: p2
- Higher temperatures and less rainfall would result in some plant species failing to survive, leading to drought-resistant species (xerophytes, Figure 5) becoming more dominant.
The loss of non-drought-resistant species of plants would lead to the loss of some animal species dependent on them as a food source.
These would be replaced by other species that feed on the xerophytes. - Insect life cycles and populations will change as they adapt to climate change. Insects are key pollinators of many plants, so if the range of an insect changes, it could affect the lives of the plants it leaves behind, causing extinction.
And as insects carry many plant and animal pathogens, if tropical insects spread, this in turn could lead to the spread of tropical diseases towards the poles. - If climate change is slow, species may have time to adapt (for example by eating a different food source) or to migrate to new areas.
This will lead to a loss of native species, but in turn other species may move into the area - so biodiversity would not necessarily be lost.
The species mix would simply change.
Loss of biodiversity in the uk
Scientists have estimated that the present worldwide rate of extinction is between 100 and 1000 times greater than at any other point in evolutionary history.
This is primarily the result of the increase in the world human population.
This has resulted in large areas of land being cleared worldwide, to meet the demand for food.
Twelve to fifteen million hectares of forest are lost worldwide each year - the equivalent of 36 football fields per minute.
These highly diverse habitats are replaced with agricultural land, which has far lower levels of biodiversity.
Conservation agencies have estimated the percentage of various habitats that have been lost in the UK since 1900.
Their findings are summarised in Table 1.
Reasons for maintaining biodiversity:
Aesthetic reasons
Economic reasons:
Ecological reasons
Aesthetic reasons:
The presence of different plants and animals in our environment enriches our lives. For example, you might like to relax on a beach, walk in your local woodland or park or visit a rainforest.
The natural world provides inspiration for people such as musicians and writers, who in turn provide pleasure for many others through music and books.
Studies have shown that patients recover more rapidly from stress and injury when they are supported by plants and a relatively natural environment.
Economic reasons: p1
If biodiversity in an ecosystem is maintained, levels of long-term productivity are higher.
Soil erosion and desertification may occur as a result of deforestation. These reduce a country’s ability to grow crops and feed its people, which can lead to resource- and economic-dependence on other nations.
It is important to conserve all organisms that we use to make things. Non-sustainable removal of resources, such as hardwood timber, will eventually lead to the collapse of industry in an area.
Once all or enough of the raw material has been lost, it does not become economically viable to continue the industry.
Note that even when ‘sustainable’ methods are used - for example replanting forest areas - the new areas will not be as biodiverse as the established habitats they replace.
Large-scale habitat and biodiversity losses mean that species with potential economic importance may become extinct before they are even discovered.
For example, undiscovered species in tropical rainforests may be chemically or medically useful.
A number of marine species use a chemical-based defence mechanism.
These are rich potential sources of new and economically important medicines.
Economic reasons: p2
- Continuous monoculture results in soil depletion - a reduction in the diversity of soil nutrients.
It happens because the crop takes the same nutrients out of the soil year after year and is then harvested, not left for the nutrients to be recycled.
This depletion of soil nutrients makes the ecosystem more fragile.
The crops it can support will be weaker, increasing vulnerability to opportunistic insects, plant competitors, and microorganisms.
The farmer will become increasingly dependent on expensive pesticides, herbicides, and fertilisers in order to maintain productivity. - High biodiversity provides protection against abiotic stresses (including extreme weather and natural disasters) and disease.
When biodiversity is not maintained, a change in conditions or a disease can destroy entire crops.
The Irish potato famine of the 1840s was a direct consequence of the reliance on only two varieties of potato.
When a new disease spread to the area (the oomycete Phytophthora infestans), neither species contained alleles for genetic resistance, so the entire crop was destroyed.
This led to widespread famine and the deaths of around 1 million people
Economic reasons: p3
Areas rich in biodiversity provide a pleasing, attractive environment that people can enjoy.
Highly biodiverse areas can promote tourism in the region, with its associated economic advantages.
The greater the diversity in an ecosystem, the greater the potential for the manufacture of different products in the future.
These products may be beneficial to humans.
For example, it may make food production more financially viable or provide cures or treatment for disease.
Plant varieties are needed for cross breeding.
which can lead to better characteristics such as disease resistance or increased yield.
The wild relatives of cultivated crop plants provide an invaluable reservoir of genetic material to aid the production of new varieties of crops.
Also, through genetic engineering, scientists aim to use genes from wild plants and animals to make crop plants and animals more efficient, thus reducing the land required to feed more people.
If these wild varieties are lost, the crop plants may themselves also become more vulnerable to extinction.
This is also important ecologically.
Ecological reasons p1
All organisms are interdependent on others for their survival.
The removal of one species may have a significant effect on others, for example a food source or a place to live may be lost.
For example, decomposers break down dead plant and animal remains, releasing nutrients into the soil, which plants later use for healthy growth.
Plants rely on bees for pollination - this is important for both wild plant species and commercially produced crops.
Fruit farmers use bees to pollinate their crops; a decrease in the wild bee population would decrease crop yields.
Ecological reasons p2
Some species play a key role in maintaining the structure of an ecological community.
These are known as keystone species.
They have a disproportionately large effect on their environment relative to their abundance (in terms of their biomass or productivity).
They affect many other organisms in an ecosystem and help to determine the species richness and evenness in the community.
When a keystone species is removed the habitat is drastically changed. All other species are affected and some may disappear altogether.
It is therefore essential to protect keystone species to maintain biodiversity.
Human activity versus biodiversity:
- human activity also plays an important role in increasing biodiversity.
- In many countries, including the UK, the natural habitat is created by human intervention and the management of land.
- For example, farming. grazing, planting of hedges, meadows, and forest management have changed the landscapes, the habitats and the ecology over thousands of years.
- Even the wildest of habitats, such as Dartmoor and the Scottish mountains, are a result of farmers and landowners managing the ecosystems.
- One example is sheep grazing on downlands.
- This enables rare species like the Glanville fritillary (an orange patterned butterfly) to survive.
- By maintaining the grass at low levels it allows the plantains that the caterpillars feed on to thrive and therefore maintains biodiversity.
- research has also shown that after annual controlled burning of gorse and heather in the New Forest (an area of lowland heath), biodiversity soars.
- If left to its own devices, bracken and pioneer tree species such as pine and silver birch would start to dominate.
- Areas of lowland heath worldwide are now rarer than rainforest and provide habitats for rare UK bird and reptile species such as the nightjar and sand lizard.
Keystone species:
Sea stars, American alligators and prairie dogs are all examples of key stone species:
Like many keystone species, sea stars are predators.
Alligators make burrows for nesting and to stay warm.
It is estimated that up to 200 species rely on prairie-dog colonies, primarily due to their tunnelling activities.
Like many keystone species, sea stars are predators.
They maintain a balanced ecosystem by limiting the population of other species. Sea stars eat mussels and sea urchins, which have no other natural predators.
If the sea star is removed from the ecosystem, the mussels undergo a population explosion, reducing the number of other species present in an area (such as barnacles and limpets) as they compete for space and other resources.
Similarly, if sea urchins are not eaten, their growing population crowds coral reefs, preventing other species from occupying the same area.
