Changes in biodiversity are caused by a range of drivers. A driver
1x is any natural or human-induced factor that directly or indirectly causes a change in an ecosystem. The graph pictured shows the
impact of drivers on the biodiversity of different biomes. The cell color indicates the impact to date of each driver on biodiversity in each biome over the past 50-100 years. The arrows indicate the trend in the impact of the driver on biodiversity. Horizontal arrows indicate a continuation of the current level of impact; diagonal and vertical arrows indicate progressively increasing trends in impact. Consider the polar biome. Which driver is having the greatest impact on the biodiversity of this biome?
1x
A
overexploitation
1x
B
pollution
1x
C
climate change
1x
D
habitat change





The polar bear is one of the 10 most endangered species in the
×
US, critically threatened by the effects of human population. A polar bear is fit to swim 100 miles for food, in search of mates or,
more recently, just some ice to stand on. With five inches of blubber keeping this enormous bear prepared for subzero temperatures, the largest member of the bear family has remarkably adapted to Arctic conditions.
Based on the biodiversity data offered in the graph and what you know of human impacts on the environment, what is most likely to the greatest threat to polar bears?
1x
A
Polar bears are losing habitat to expanding human population growth.
x
B
Polar bears are nearing extinction due to the extreme impacts that human-caused climate change has had on the Arctic.
1x
C
Polar bears are losing food sources due to overfishing in the area.
1x
D
Polar bears are facing extinction due to effects of the ozone hole over the Arctic region.