Species and their vulnerability to extinction

Before species become extinct they become rare. Rarity is assessed by three criteria:

Endemic species often fit these criteria and many are in danger of extinction around the world.

8.1 The Iberian lynx, endemic to Iberian peninsula in Spain, is down to 100 cats due to habitat loss

Endemic species -species naturally found only in a single geographic area

-expansions caused by humans are not considered part of the species natural distribution Exs. 1)giant panda is endemic to China even though they are in zoos around the world 2)English plantain is endemic to Europe and Asia but is now found throughout the world because its fruits are easily dispersed. Black locust is a native to eastern and southern US but is widely planted elsewhere in North America

-evolved in that region and nowhere else

-isolated areas like remote islands, old lakes, and solitary mountain peaks often have high endemism. Also high in geologically old, continental areas with Mediterranean climates like South Africa and California. In Texas, the Edwards Plateau and Trans Pecos are areas of high endemism.

Texas is ranked 4th in the USA in numbers of endemic plant species. It has 379 and only CA, HI, and FL have more

Table 8.1, Figure 8.2

-Madagascar is an example of a hot spot for endemism outside the USA

-80% of land altered or destroyed by humans putting about 1/2 of endemic bird and mammal species in danger of extinction

-93% of mammal species (28 species of lemurs)

-99% of 144 species of frogs

-90+% of 1500 plant species

8.2 The number of plant species endemic to the different states varies greatly

Species are most vulnerable to extinction for five reasons

Species of desert pupfish of the southwestern U.S. are highly endangered

8.3 Dried ginseng roots are used for traditional Chinese medicine as an aphrodisiac and tonic

10 categories of species closely linked with extinction

1. Species that need a large home range.

Ex. Brown and Grizzly bears

2. Animal species with a large body size.

-have large home ranges, require more food, and are more easily hunted by humans

Ex. Sri Lanka (Ceylon) -large island off the southern coast of India. Largest species of carnivores (leopards and eagles) and the largest species of herbivores (elephants and deer) are currently at the greatest risk for extinction

Fig. 8.4

3. Species that are not effective dispersers.

-environmental changes by humans are rapid enough that adaptation may be prevented and migration is the only solution Ex. A detailed analysis of vertebrates of western Australia revealed that modern extinctions were almost exclusively confined to nonflying mammals with few occurring in birds and bats

8.4 Body mass of herbivorous mammals that survived arrival of European people (green) and those that went extinct (red).

4. Species that are seasonal migrants.

-depend on two or more distinct habitat types. If either is damaged, the species may be unable to persist. Ex. neotropical migrants -billions of songbirds of 120 species that migrate between the northern USA and the American Tropics

 

5. Species with little genetic variability.

-genetic variability may allow for adaptation to change. When it is low it can lead to extinction Ex. Primary reason that cheetah is believed to have low disease resistance

 

6. Species with specialized niche requirements.

-Ex. wetland plants may need very specific and regular changes in water level

-Ex. salt marsh cord grass is found only in salt marshes

-Ocellated antbird feeds only on insects and other small animals fleeing from army ants

Fig. 8.5

8.5 Ocellated antbird feeds only on insects and other small animals fleeing from army ants.

7. Species that are characteristically found in stable, pristine environments

Box 8.1 Why are frogs and toads croaking? Below an Australian frog is tested for chytrid fungi:

 

8. Species that form permanent or temporary aggregations.

Ex. herds bison, flocks passenger pigeons, bat roosts, sea turtles

Allee effect-inability of social animals to forage, find mates, or defend territory when populations are small

 

9. Species that evolved in isolation and had no prior contact with people.

Ex. Rates of recent bird extinction is far lower on Pacific Islands colonized by Polynesians than on islands not colonized by Polynesians

10.Species that have closely related species that are recently extinct or are threatened with extinction.

-characteristics that make certain species vulnerable are often shared by related species

Ex. Sea turtle species are hunted, migrants, and form temporary aggregations. Because of this they often suffer from the small population and declining population paradigms

Conservation categories

-developed by the International Union for the Conservation of Nature (IUCN)

-developed categories based on available data

1) observable decline in numbers

 

2) range of species

 

3) total number of mature individuals

 

4) expected decline in number of individuals if the population decline or habitat destruction continues

 

5) probability of extinction in a certain amount of time

8.6 The IUCN categories of conservation status

IUCN has evaluated most bird, amphibian,and mammal speciesbut the levels of evaluation are lower for reptiles, fish, and angiosperms resulting in low apparent levels of threat Fig. 8.7

U.S. Endangered Species Act of 1973Basics of the law:-to "provide a means whereby the ecosystem upon which endangered and threatened species depend may be conserved [and] to provide a program for the conservation of such species"-by law, endangered and threatened mean the following:1) endangered-those likely to become extinct as a result of human activity and natural causes in all or a major portion of their range2) threatened- those likely to become extinct in the near future  -requires all U.S. government agencies to consult with the USFWS and National Marine Fisheries Service to determine whether their activities will affect listed species -also prevents private individuals, businesses and local governments from harming listed species and their habitats. Fines for individuals are up to $100,000 and one years imprisonment or up to $200,000 for organizations

-at extremes are overzealous USFWS employees and landowners who destroy endangered species on their property "shoot, shovel, and shut up" or those that criticize it for halting development or costing too much Ex. Development criticism- 1987-1992 @ 100,000 cases (98,237) presented involving ESA. About 50 (55) projects were stopped cold. Much less than 1% (5/100 of 1%) Ex. Cost criticism- USFWS annually spends around 350 million on activities related to the act with the largest portion being land acquisition and legal expenses. From 1977-1995, the average annual funding was 39 million per year. This is 16 cents per taxpayer per year or the cost of one mile of interstate highway. The number of species protected by the ESA has been increasing at a faster rate than funding. Probably need $650 million per year to create a truly effective program.

Since 1973, more than 1519 (1500) U.S. species have been added to the list including many well-known species such as the whooping crane Fig. 8.9

-most are plants and vertebrates with invertebrates mostly disregarded (Ex. Only 70 insect species in U.S. are listed)-on average, animals are listed when about 1000 or less individuals remain and plants when fewer than 120 individuals remain

-must get data earlier and list before numbers are so low that success is unlikely

-in the USA, Natural Heritage Data Centers have provided more timely data

Figure 8.9 Whooping cranes are protected by the U.S. Endangered Species Act and are intensively managed

USA

-has Natural Heritage Data Centers (NHDC) in 50 states, three provinces in Canada, and 14 Latin American countries. NHDC is strongly supported by the Nature Conservancy.

-data is available on NatureServe website

-many of the species that are threatened or vulnerable are associated with freshwater wetlands

 

Figure 8.10

In USA, freshwater wetland species have from 40-70% of their animals (mussels, crayfish, amphibians, and fish) that are extinct or critically imperiled to vulnerable.

One third of flowering plant species are extinct or critically imperiled to vulnerable. and about ¼ of conifers and ferns.

Texas also has data on threatened and endangered species at the Texas Parks and Wildlife website

8.8 Some species groups from the United States ranked as critically imperiled, imperiled, or vulnerable