3-15 threat analysis

Question 1

Tools to assess threats

Answer 1

• Observation
• Manipulative experiments
• Need randomization, controls, and replication
• Modeling
• Using population data  expected threats

Question 2

threat analysis purpose

Answer 2

ow need to know what are the problems for a population and
where in their life cycle these occur
* Often obvious, but also often hidden threats. So need to assess
what these are and their relative importance

Question 3

Name some hidden threats. What kind might be more hidden?

Question 4

Red-cockaded Woodpecker

Answer 4

An example of where simple observation tells us what the threat is: since they
nest only in mature longleaf pines, the threat to them is the widespread loss of
those forests for paper manufacture.
Only remedy: preserve old-growth longleaf pine forests

Question 5

areas of highest biodiversity?

Answer 5

oceans

Question 6

coral reefs

Answer 6

• Tremendous diversity: millions of species
• ¾ of world reefs threatened or lost

Question 7

three major threats to world reefs

Answer 7

• Pollution because usually close to land: silt smothers, oversupply
  of nutrients  algal overgrowth, pesticides, industrial waste, oil
• Climate change: increasing T, decreasing pH
• Overfishing for food and aquarium trade

Question 8

possible solutions to coral reef threats

Answer 8

• Reducing nutrients by e.g. better waste treatment
• Erosion control
• Restrictions on fishing
• Climate mitigation

Question 9

problems of possible solutions to coral reef threats

Answer 9

cost and resistance

Question 10

Mumby et al.

Answer 10

observational study of threats to coral reefs
Looked at role of overfishing by comparing a recovery of corals in a Bahamas marine reserve vs. outside the reserve
Knew more parrotfish in “no-take” zones, so compared with “take” zones – replicated and randomized
Other possible factors: cover of corals, type of corals, larval coral-eating fish density (damselfish)  no correlation
Parrotfish important grazers
on algae in coral reefs
Algae will cover corals and
block settlement of coral
larvae
So parrotfish indirectly
enhance coral growth

Question 11

Miller et al.

Answer 11

manipulative experiment that tested effects of nutrient supply and predation on algal growth
Hypothesis: two threats:
1. Excess nutrients, so natural environment vs. enrichment with nutrients
2. Grazing by parrot fish, which feed on algae growing on corals, so caged half of treatments

Question 12

Use of models

Answer 12

Model using population growth analysis
Threats to sea turtles: beach predation, shrimp fishing nets
Seven stages: (1) eggs/hatchlings, (2) small juveniles, (3) large juveniles, (4) subadults,
(5) novice breeders, (6) first year returnees, (7) mature breeders (after 22 years)
How carried out? No of eggs, hatching success, survival and return of marked turtles

Question 13

Archie Carr