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U316 The Environmental Web

Block 2: Biodiversity and Ecosystems


Chapter 1 A living world

Biting the apple
Biodiversity and ecosystems: the environmental issues
Species and extinction
Ecosystem functions
How do we value species?

Chapter 2 A global perspective on people and ecosystems

Introduction to World Resources: The Fraying Web of Life
WR Chapter 1: Linking people and ecosystems

Chapter 3 Threats to ecosystems and biodiversity

What threats?
Further thoughts about ecosystems

Chapter 4 Biodiversity in your own backyard

Biodiversity at the local level
How biodiversity has been measured in the UK
'Hands-on' biodiversity recording and statistical analysis

Chapter 5 Action plans

Biodiversity Action Plans
Habitat action plans
Single-species BAPs
Business and biodiversity
The changing face of agriculture - action to protect biodiversity in the wider countryside


Biological Records Centre

British Dragonfly Society

British Trust for Ornithology

Butterfly Conservation

Conservation International

Countryside Survey 2000

Global Diversity Information Facility

Integrated Taxonomic Information System

National Biodiversity Network

The Tree of Life Web Project

UK Biodiversity Action Plan

UN Environment Programme

World Resources Institute

All Routes Block 2 Links

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Block 1 Environmental Changes: Global ChallengesBlock 3 Climate Change: From Science to Sustainability
Block 4 Sustainability and Water ManagementBack to U316

Chapter 1

Biodiversity, broadly defined, is all hereditarily based variation from genes, through species to ecosystems. A narrower definition that equates biodiversity with the number of species in an area is often used.

The collection of species in a particular habitat is described as a community, and a community plus its non-living physical environment comprises an ecosystem. The living and non-living components of ecosystems are linked by transfers of carbon and other chemical elements between them.

There are three kinds of reason why biodiversity matters to people; its aesthetic value, its utility and moral reasons. In addition to the direct value of species that provide goods, such as food and timber, biodiversity plays a part in the services that ecosystems provide. Examples of ecosystem services are as storage reservoirs in the carbon cycle and in water processing.

According to the biological species concept, a species is defined as a distinct biological entity that does not interbreed with other species.

Species extinction is a normal evolutionary process, but the high proportion of species that are threatened with extinction today suggests that human actions are leading to a mass extinction of crisis proportions. The consequences of these extinctions for ecosystem function will depend on which speices are affected and what role they play. In addition to the use-value of crops and species harvested from the wild, biodiversity at the genetic level of organization has value because crops lacking genetic diversity are particularly susceptible to disease.

Chapter 2

Chapter 1 of WR, 'Linking people and ecosystems;, argues that human well-being and the global economy are both underpinned by the goods and services provided by ecosystems.

Examples of goods include food and fibre crops, fish, timber and genetic resources for crop breeding. Examples of services provided by ecosystems include watershed protection and climate control, crop pollination, soil production and carbon sequestration.

Decisions about how to manage ecosystems involve trade-offs between the costs and benefits of any action.

Ecosystems may collapse if exploitation pushes them over a threshold of sustainability.

Amongst other threats, natural ecosystems can be degraded by overharvesting (eg overfishing), conversion to cropland or urban use, soil erosion and overexploitation of groundwater.

Invation by non-native organisms also threatens biodiversity in many ecosystems.

The ownership of resources (or ecosystems) affects how they are exploited and whether exploitation is sustainable or not.

How ecosystems may be managed for sustainable production, in general, requires further research.

Chapter 3

From reading WR Chapter 2, you obtained an expert assessment of the state of major ecosystems with respect to their capacity to provide goods and services, including biodiversity, that are important for human welfare. Despite weaknesses in the WR appraoch, it provides the best global assessment so far - but you need to be aware of its limitations.

The case studies in WR Chapter 3 provide examples that illustrate the difficulties of trying to improve damaged ecosystems. For ecosystem remediation, the social and political context becomes dominant, with land ownership and governance of central importance.

Both top-down (eg Florida Everglades, Mongolian grasslands) and bottom-up (eg Mankote, Bolinae, Dhani Forest) approaches have been used in ecosystem renovation projects.

For coastal ecosystems, as broadly defined in WR, the main threats to global biodiversity are conversion, pollution and habitat destruction or damage. The widespread bleaching of coral reefs suggests that they may be especially sensitive to climate change.

Conversion is th emain threat to global forest diversity, with disturbance, habitat fragmentation and invasive species as significan secondary threats. The long period of time needed to develop a species-rich forest underlines the importance of conserving ancient forests.

Freshwater ecosystems are possibly the most crucial for human survival and are also the most vulnerable to damage and the most strongly influenced by other ecosystems. Their biodiversity is in the worst state of all the types of ecosystem assessed in WR, with pollution, damage and invasive (alien) species identified as the major threats.

In grassland ecosystems (broadly defined to include tundra in WR), conversion has been the major cause of biodiversity loss, followed by habitat fragmentation and damage or destruction. Desertification is a significant problem, often cuased by overuse (eg overgrazing) possibly in combination with climate change.

Just as individuals within species interact, so that a threat to one species may escalate into a threat to many, so ecosystems influence each other. Freshwater ecosystems are affected directly or indirectly by nearly all other types, and the outputs from urban ecosystems similarly affect all others.

In the longer term the impact of climate change on biodiversity and ecosystems could be the greatest threat of all. Ecological effects at all levels, from individuals to ecosystems, have been identified but it is still too early to attribute any species' extinctions directly to climate change. The higher level impacts (on communities and ecosystems) are especially difficult to determine and quantify.

Chapter 4

Biodiversity is present on the local scale within the UK as well as in areas commonly associated with biodiversity such as rainforests or coral reefs.

There are certain habitats and species that the UK has particular international responsibilities to protect. These include veteran trees and estuaries.

Introduced species such as the trees grown in conifer plantations produce a much less biodiverse ecosystem than the native braodleaved woodland.

Biodiversity has been measured in the UK over a long period by highly dedicated amateurs such as members of the Botanical Society of the British Isles. There have been national surveys of several groups of organism on at least two dates allowing a detailed picture of change in abundance over time to be built up.

To more fully understand change in biodiversity it is necesary to develop a hypothesis that might explain the changes then collect data and carry out statistical analysis. As with any environmental information, data from biodiversity surveys show considerable variation around any mean values, making it difficult to see any overall differences.

Statistical techniques such as correlation and regression can be used to cut through this variation. These statistical tests give a significance level which is an indication of how likely the null (ie no difference) hypothesis is to be true. If there is a very low probability that the null hypothesis is true then there are real differences that the original hypothesis may help to explain.

Two hypotheses that deal with differing patterns of biodiversity are described in the chapter. The overlapping hotspots hypothesis asks if several different groups of organism all have their biodiversity hotspots in the same area; if true it has significant implications for designating which areas are set up as protected areas. The species-energy hypothesis predicts that the number of species is related to the amount of solar energy, with the region nearest the Equator receiving more energy and hence having more species.

It is possible to use various geographical grid systems to locate points on Earth when carrying out species surveys. The British Ordnance Survey system uses a scale of metres east or north of an origin point just south of the Scilly Isles.

Chapter 5

Biodiversity Action Plans were originally developed in response to the 1992 Earth Summit in Rio. They have become one of the main ways of protecting the environment in the UK.

Habitat action plans have been prepared for all priority habitats (habitats of high conservation concern), eg reedbeds. Plans may lead to the protection of existing areas of these habitats and the establishment of new areas of these habitats.

Individual species have action plans for a variety of reasons but mainly either because they are very rare or because they are in sharp decline. To develop good action plans for individual species, detailed monitoring and modelling of population variability would ideally be available. However, this takes many years of detailed measurements. An example of a species with a BAP is the natterjack toad.

Local action plans have been developed by a wide range of different organizations to protect the local habitats and species. These plans are partly designed to help meet national targets for species and habitat conservation.

Many businesses can have large negative effects on the environment. A variety of large and small companies have developed plans to minimize their impact. Some have found that developing a BAP increases overall efficiency by reducing waste and creating a better environment to work in.

Agriculatural intensification was the biggest threat to biodiversity in the UK during the 20th century. This intensification was often fuelled by government subsidies. There is now greater emphasis on sustainability which may benefit biodiversity or at least reduce its rate of loss.