Chapter 57: Conservation Biology • Overview of the Biodiversity Crisis • Losing Biodiversity • Vulnerable Species • Species Endemism and Hotspots • Costs of Extinction, Ecosystem Services • Factors Responsible for Extinction • Introduced Species • Ecosystem Disruption • Perils of Small Population Size • Preserving Endangered Species • Conservation Whole Ecosystems
Overview of the Biodiversity Crisis As much as 20% of the world’s biodiversity may be lost during the next 30 years (and 50-66% by the end of the century): - 50000 out of 250000 plant species - 4000 out of 20000 butterfly species - 2000 out of 9000 bird species • SLIDE SHOW on biodiversity crisis at http://io.uwinnipeg.ca/~simmons/CHAP5598/sld001.htm BUT we may lose even more unknown species, because no more than 15% of the world’s eukaryotic organisms have been described yet. Question: how much of Stellenbosch’s University books or buildings would you burn?
The new science of conservation biology • we are in the midst of one of the great extinction events in earth’s history • concerned biologists have come together to use their knowledge to save species from extinction • this emerging discipline has been called CONSERVATION BIOLOGY
Prehistoric and historic extinctions • Extinction due to prehistoric humans Shortly after humans arrived, 74-86% of large animal species became extinct. • caused by hunting and habitat alteration (e.g. fires to replace forest with grasslands) • Extinctions in historical time since 1600 Historical extinction rates are best known for birds (~ 113 species) and mammals (~ 85 species) => this rate of extinction is increasing due to human activities = BIODIVERSITY CRISIS
Historic extinctions Tasmanian Tiger (1936) Dodo (1681) Carolina Parakeet (1918)
Island species are particularly vulnerable The majority of historic extinctions have occurred on islands because • island species have small populations • island species often do not have any behavioural defenses against introduced predators or immunological defenses against introduced diseases • island species were outcompeted for resources by introduced species
The snake that ate all the birds • If you visit the island of Guam, you won't see the Mariana Fruit Dove, Guam Flycatcher, Rufous Fantail, Cardinal Honeyeater, or Guam Rail. They have become extinct since the late 1940s, when the Brown Tree Snake is believed to have first colonized the island. Guam Rail, extinct in the wild because of snake predation
Species Endemism and Hot Spots • A species found naturally in only one geographic area is termed endemic • Isolated geographical areas, such as islands, lakes or mountain ranges, often have many endemic species • Notable hotspots of endemism are Madagascar, SE Asia, the Caribbean, and SOUTH AFRICA! • Unfortunately, many experiencing high rates of habitat destruction
Endemism hotspots contain many species and many humans By protecting just 1.4% of the world’s land surface containing all the endemism hotspots, 44% of the world’s vascular plants and 35% of its terrestrial vertebrates could be preserved. BUT, these hotspots also contain 20% of the world’s population, most of them rapidly increasing, and are therefore areas of intense commercial exploitation and habitat destruction. => Therefore, successful conservation cannot focus on wilderness areas alone!
1. Losing Biodiversity incurs huge costs Direct economic value • production of foods, fibres, fuels, medicines • maintainance of biodiversity (gene prospecting) Rosy periwinkle
2. Losing Biodiversity incurs huge costs Indirect economic value • purification of air and water • mitigation of droughts and floods • generation and preservation of soils and renewal of their fertility • detoxification and decomposition of wastes • pollination of crops and natural vegetation • dispersal of seeds • cycling and movement of nutrients • control of the vast majority of potential agricultural pests • protection of coastal shores from erosion by waves • partial stabilization of local, regional and global climate • moderation of weather extremes and their impacts
Economic value of intact habitats Mangrove, Thailand Tropical forest, Cameroon 3,000 80,000 60,000 2,000 Economic value (US$ per hectare) 40,000 Economic value (US$ per hectare) 1,000 20,000 0 Reduced- impact logging Small- scale farming 0 -1,000 Intact Shrimp farming Plantation -2,000 The total economic value of intact natural habitats (accounting for all the economic benefits they produce) is often much higher than that of converted habitats => special business interests of small groups of stakeholders, such as large international timber corporations, put their interests above those of the common good
6000000000 dollars per year … … earned by bees and other pollinators in the United States alone
3. Losing Biodiversity incurs huge costs Ethical and aesthetic value · provision of aesthetic beauty and intellectual stimulation that lift the human spirit · future generations have the right to enjoy the same benefits from biodiversity and ecosystem services as we do
Where would you like to go on vacation? Here or …
4. Losing Biodiversity incurs huge costs Consequences of biodiversity loss · loss of genetic diversity and the opportunity to use it for crops, medicines, etc. · droughts and floods · soil erosion, and land slides · desertification, mineralization and water logging of productive lands · polluted water, loss of water · crop loss due to decrease of pollinators, seed dispersers and biological control · coastal erosion (storm and tsunami damage) · some rather angry and disappointed children
12000000000 dollars lost in the Mississippi floods in 1993
Extinction Crisis • Factors responsible for extinction: • Habitat loss • Habitat fragmentation • Overexploitation (hunting, fishing ..) • Introduced species • Disruption of ecological interactions • Pollution • Loss of genetic variability due to small populations • Catastrophic disturbances (storms, floods, etc.)
Habitat Loss • Natural habitats adversely affected by human influences in four ways: • destruction • clear-cut tree harvesting • pollution • habitat degradation, • e.g. acid rain • disruption • park visitors - habitat fragmentation
Fig. 57.12(TE Art) 0.5 0.4 0.3 Extinction rate (per year) 0.2 0.1 0.0 10-2 1 102 Area (km2) The smaller the islands, the larger the risk of extinction for bird species.
Habitat Loss • Habitat fragmentation • fragmenting of population into unconnected patches • Edge effects can significantly alter the microclimate near the edge and may reduce appropriate habitat for many species. • Expanding edges opens up opportunities for parasites and predators to invade new areas.
Long edges decrease the value of habitat fragments because conditions in edges are different The effects of fragmentation can be alleviated if the habitats between the fragments are allowing animals at least to move through them
Fragmentation of a Woodland Habitat in Wisconsin, USA Less total area, less area per patch, more edges, longer distance between patches => All making it harder for forest specialists to survive
Case Study 3: North American songbirds • In many areas of the eastern USA, more than 75% of migrant bird species have experienced a significant decline. Species experiencing the greatest declines are those which are both long-distance migrants and deep forest dwellers. The reasons are two-fold: • Forest fragmentation and loss both on • wooded summer nesting grounds • winter habitats in Central and South America • Increased brood parasitism by cowbirds along forest edges American Redstart
Case Study 4: Overexploitation of whales Commercial whaling began in sixteenth century and reached its height in early 20th century. • As whalers reduced the numbers of one species, they simply switched species. • In 1974, the International Whaling Commission (IWC) banned hunting on all blue, gray, and humpback whales and instituted partial bans on others. • 1986 - worldwide moratorium • as a result, some species have recovered, but others have not
As whalers reduced the numbers of one species, they simply switched species.
Ecosystem Disruption Species often become vulnerable to extinction when their web of ecological interactions becomes disrupted. • e.g. commercial whaling initiated a series of changes causing disastrous effects on kelp forests Whales down -> zooplankton up -> pollock fish up -> herring and perch down -> sea lions and seals down -> orcas switch to sea otters -> sea urchins up -> kelp forest and fish living there down => complex interaction of top-down and bottom-up effects
Introduced Species • Detrimental effects • Natural or man-made colonization may bring together species with no previous history of interaction which may lead to extinction • Damage to human economy and health • Effects of introductions on humans has been enormous. • Non-native species cost US economy alone $140 billion annually.
Case study 5: Avian extinctions on Hawaii • Goats and more than ten other introduced mammals have drastically altered the flora and fauna of Hawaii
In addition, avian malaria was introduced to which native Hawaiian bird species have no resistance
As a consequence, the Akiapolaau and many other Hawaiian bird species are endangered or already extinct
Efforts to combat introduced species • 1. Eradication • difficult, expensive, time-consuming, and potentially impossible, but possible on small islands • 2. Prevention • needs strong policies and enforcement, e.g. inspection of shipments, tourists • e.g. http://academic.sun.ac.za/cib/
Preserving Keystone Species • Keystone species are usually characterized by the strength of their impact on their community, ensuring the structure and functioning of an ecosystem • Community importance = change in some quantity of the ecosystem (e.g. species richness) per unit change in keystone numbers • e.g. flying foxes
Cascading extinctions • Flying foxes are driven to extinction by forest loss and human persecutation • The function of flying foxes in their ecosystem, i.e. pollination and seed dispersal, is lost • Consequently, all the plants depending on them for pollination and seed dispersal are losing out • With the plants, all the animals, e.g. insect herbivores, are disappearing, too => Ecosystem disruption leads to a much simpler, species-poor ecosystem
The Perils of Small Population Size- or the Downward Spiral towards Extinction • 1. Demographic factors • By nature of their small size, small populations are ill equipped to withstand a catastrophic event (density-independent effects), e.g. fires, storms, etc. • Remaining individuals may all be old males • 2. Lack of genetic variability • Small populations are prone to the loss of genetic variation as a result of genetic drift, making them susceptible to disease
The Perils of Small Population Size- or the Extinction Vortex • 3. Spatial effects • Individuals may simply not find each other anymore to mate, e.g. tigers with large home ranges (the Allee effect) • 4. Metapopulation breakdown • Small and fragmented populations are not connected anymore, so suitable habitat is not re-colonized by immigrants from other habitat patches anymore
Preserving Endangered Species • Preservation approaches: • habitat restoration • pristine restoration • removal of introduced species • cleanup and rehabilitation • captive breeding
Conserving Whole Ecosystems Isolated patches of habitat lose species much more rapidly than large areas: - habitat loss and fragmentation - species-area effect and island biogeography • Mega-reserves are large areas of land that contain a core of one or more undisturbed habitats. • focus on preserving intact ecosystems
This lecture will NOT be part of the exam! • EXAM includes • All 9 ecology lectures except today’s • Corresponds with chapters 53 - 56 plus the lectures on South African biomes • 45 marks = 25 marks are multiple choice questions and 20 marks are essay questions (4 questions for 4 - 6 marks) • Marks are almost evenly distributed among chapters Thank you and good luck!