Environmental Problems, Their Causes, and Sustainability 1

Characteristics ofSuccessfulInvader Species• High reproductive rate,short generation time(r-selected species)• Pioneer species• Long lived• High dispersal rate• Release growth-inhibitingchemicals into soil• Generalists• High genetic variabilityCharacteristics ofEcosystems Vulnerableto Invader Species• Similar climate to habitatof invader• Absence of predators oninvading species• Early successionalsystems• Low diversity of nativespecies• Absence of fire• Disturbed by humanactivitiesFigure 12-12 Threats to natural capital: some general characteristicsof successful invader species and ecosystems vulnerableto invading species.breed rapidly. We also need to remind ourselves thatthe globalization of our economies and lifestyles iswhat helps bring these new and unwanted biologicalimmigrants into countries throughout the world.Case Study: Exploding Deer Populationsin the United States: Should We Put Bambion Birth Control?In suburban areas we can trap and move deer somewhereelse, put them on birth control, sterilize them,or not plant their favorite foods around houses.Arelated problem is the explosion of deer populationsin suburban areas. In this case we are the invaderspecies. Americans have increasingly moved into thewoods habitat of deer and provided them with flowers,garden crops, and other plants they like to eat.Deer are edge species that like to live in the woodsfor security and venture into nearby fields, lawns, orgardens for food. Suburbanization has created an allyou-can-eatedge paradise for deer. The deer also raidnearby farmers’ fields and orchards, threaten rareplants and animals in some areas, and spread Lymedisease (carried by deer ticks) to humans.You may be surprised to learn that deer kill andinjure more people each year in the United States thanany other wild species. Collisions between deer andvehicles occur more than 1.5 million times each year,injure thousands of people, typically kill at least 200people annually, and cause more than $1 billion in additionaldamages.There are no easy answers to the deer populationproblem in the suburbs. Increased hunting—by changinghunting rules to allow killing of more female deer(does)—can cut down the overall deer population. Butthis will have little effect on deer living near suburbanareas because it is too dangerous to allow huntingthere. Deer could also be trapped and moved somewhereelse, but this is expensive and must be repeatedevery few years. And where are we going to take them?Darts loaded with deer contraceptive could befired into does each year to hold down the birth rate.But this is also expensive and must be repeated eachyear. One possibility is an experimental single-shotcontraceptive vaccine that causes does to stop producingeggs for several years. Another approach, beingtested by state biologists in Connecticut, is to trapdominant males and use chemical injections to sterilizethem. However, both these approaches will requireyears of testing.Meanwhile, if you live in the suburbs, expect deerto chow down on your shrubs, flowers, and gardenplants. They have to eat every day like you do. Youmight consider not planting their favorite foodsaround your house.12-5 EXTINCTION THREATS FROMPOACHING AND HUNTINGHow Serious Is the Illegal Taking or Killingof Wild Species? Making Big MoneySome protected species are killed for their valuableparts or are sold live to collectors.Organized crime has moved into illegal wildlife smugglingbecause of the huge profits involved. Smugglingwildlife—including many endangered species—is thethird largest and most lucrative illegal cross-bordersmuggling activity after arms and drugs. At least twothirdsof all live animals illegally smuggled around theworld die in transit.Poverty is one reason behind the illegal smugglingof wild species. Some poor people struggling tosurvive in areas with rich stores of wildlife kill or trapsuch species to make enough money to survive andfeed their families. What would you do in the same situation?Others are professional poachers.To poachers, a live mountain gorilla is worth$150,000, a panda pelt $100,000 (only about 1,500 pandasare left in the wild), a chimpanzee $50,000, and anImperial Amazon macaw $30,000. A rhinoceros horn isworth as much as $28,600 per kilogram ($13,000 perpound) because of its use in dagger handles in theMiddle East and as a fever reducer and alleged aphrodisiacin China—the world’s largest consumer ofwildlife—and other parts of Asia.In 1950, an estimated 100,000 tigers existed in theworld. Despite international protection, today fewerthan 7,500 tigers remain in the wild (about 4,000 in India),mostly because of habitat loss and poaching for238 CHAPTER 12 Sustaining Biodiversity: The Species Approach