BIODIVERSITY 1

Introduction The species and resources on our planet are limited, but the human population is growing unchecked surge in human population will drastically affect biodiversity rapid deforestation of Borneo has had devastating effects on species like the orangutan 2

Figure 57.1 (a) Rapid deforestation of Borneo Borneo (b) Orangutans are one casualty of deforestation Samboja 300 km 3

What Is Biodiversity? Biodiversity Describes the evolutionary relationships among all forms of life branches represent all of the lineages of organisms living today tips represent all of the species When biodiversity increases, branches and tips are added to the tree  When extinctions occur, tips and perhaps branches are removed 4

Measuring and Analyzing Biodiversity Biologists recognize and analyze biodiversity at the genetic, species, and ecosystem level. Genetic diversity  The total genetic information contained within all individuals of a species 5

Measuring and Analyzing Biodiversity Species diversity  The variety of life-forms on Earth  Measured as the number and relative frequency of species in a particular region 6

Measuring and Analyzing Biodiversity  Recent efforts to document species diversity have used a new technique called bar coding well-characterized gene sequence to identify distinct species 7

Figure 57.2 Red panda Dogs: 43 Bears: 19 Seals: 36 Raccoons: 15 Badgers: 10 Weasels: 38 Otters: 8 Approximate number of species in each group Skunks: 13 8

Measuring and Analyzing Biodiversity Ecosystem diversity  variety of biotic communities in a region, along with abiotic components such as soil, water, and nutrients 9

How Many Species Are Living Today? 1.5 million species have been cataloged to date  tiny fraction of the number actually present 2 general approaches--estimate the total number of species: 1. Surveys of species-rich groups at small sites Taxon-specific surveys 2. Surveys of all the species present in a particular region All-taxa surveys 10

Taxon-Specific Surveys Example: Researchers estimated the number of insect species living in the canopy of a single tropical tree  recovered 1000 species of beetles, many previously undiscovered 11

All-Taxa Surveys Census of Marine Life  massive international effort to record the global diversity of life in the oceans  2700 scientists  30 million records (600 potentially new species) 12

5 mm 13

Where Is Biodiversity Highest? tropical rain forests are particularly species rich  7% of Earth’s land area  at least 50% of all species present Some regions of the world have a high proportion of endemic species  Species that are found in a particular area and nowhere else 14

(a) Biodiversity distribution in terms of species richness of birds (b) Biodiversity distribution in terms of endemic species of birds Number of breeding bird species per cell in grid Number of endemic bird species per cell in grid

Mapping Biodiversity Hotspots Biodiversity hotspots  at least 1500 endemic plant species  at least 70% of the traditional or primary vegetation has been lost  most urgent need of conservation action  efforts to preserve habitat would have the highest return on investment 16

Arctic tundra Boreal forest Montane grassland Temperate forest Temperate grassland Mediterranean forest Subtropical desert Tropical wet forest Tropical coniferous or dry forest Tropical grassland Galápagos Congo River basin Madagascar Borneo New Guinea Amazon 17

Threats to Biodiversity Although extinction is natural, rates of extinction are increasing Species are vanishing faster than at virtually any other time in Earth’s history  Modern rates of extinction are 100 to 1000 times greater than the average, or “background,” rate 18

Threats to Biodiversity The International Union for the Conservation of Nature (IUCN)--red list of species that are threatened with extinction  3 categories: 1. Vulnerable 2. Endangered 3. Critically Endangered 19

Birds 13% threatened Mammals 25% threatened Amphibians 41% threatened Near threatened Least concern Data deficient Critically endangered EndangeredThreatened Vulnerable 20

Threats to Biodiversity endangered species: species whose numbers have decreased so drastically that it is almost certain to go extinct without effective conservation efforts majority of biologists agree that the sixth mass extinction in the history of multicellular life is now occurring 21

Habitat Destruction Humans cause habitat destruction in many ways  Logging and burning forests  Grazing livestock  Filling in wetlands  Building housing developments 22

Habitat Destruction On a global scale, one of the most important types of habitat destruction is deforestation  As many as 3 million hectares (ha) were deforested each year in the Amazon in the 1990s 23

Habitat Destruction The total area of wet tropical forest dropped by 2.4% during 2000–2005 If this rate of tropical deforestation continues  Over 28% of the wet tropical forest that exists today will be gone in your lifetime  Including almost half of the Brazilian Amazon Forest loss in South America and Africa is particularly important because it is occurring in biodiversity hotspots 24

Figure

Habitat Degradation Habitat fragmentation  One of the most pervasive forms of habitat degradation  breakup of large, contiguous areas of natural habitat into small, isolated pieces Concerns: 1. reduce habitats to a size that is too small to support some species 26

Habitat Fragmentation 2. Fragmentation reduces the ability of individuals to disperse from one habitat to another Small, isolated populations may be more vulnerable to catastrophes Can suffer from inbreeding depression and loss of alleles due to genetic drift 3. Fragmentation creates large amounts of “edge” habitat suffer a rapid loss of species diversity and a startling drop in biomass When habitats are fragmented, the quality and quantity of habitat decline drastically 27

Habitat Fragmentation A long-term experiment in a tropical wet forest is documenting the decline in habitat quality caused by fragmentation Plots of different sizes were shown to have  A rapid loss of species diversity, especially from the smaller fragments  A startling drop in biomass, or the total amount of fixed carbon, in the study plots located near the edges of logged fragments 28

Habitat Fragmentation This experiment demonstrates that when habitats are fragmented, the quality and quantity of habitat decline drastically 29

Overexploitation  Any unsustainable removal of wildlife from the natural environment of use by humans  The dominant threat for marine species Two-thirds of harvestable marine species are depleted Overhunting has also emerged recently as a dire threat to many mammal populations in Africa and elsewhere capture of animals for the pet trade can include a wide range of species 30

Bushmeat trade 31

Invasive Species exotic species  nonnative species that is introduced into a new area  If it grows to a large population size and disrupts native species, is is considered an invasive species Global trade and travel have vastly increased the rate of exchange of plants, animals, fungi, and microorganisms 32

Exotic reptiles in Florida 33