Changes in Glacier National Park's Ecosystem

Glacier National Park has experienced notable shifts in its ecosystem over the past decade. Changes in weather patterns, such as warmer winters and drier summers, have affected plant growth. These plants, seeds, and leaf litter form the foundation of the park’s food web, supporting various herbivores. The fluctuating availability of this vegetation has influenced populations of organisms that rely on these plants as a food source, including spruce grouse, beetles, and mice.

Researchers have noted that the populations of certain herbivores, like mice and beetles, vary significantly each year. This has impacted the animals that depend on them for food, such as shrews, weasels, and red foxes. During years when plant growth is abundant, herbivore populations tend to increase, providing more food for predators. In years when plant growth is limited, herbivores decline, and predators are forced to adapt to the reduced food availability.

Additionally, human activities near Glacier National Park have affected the park’s delicate ecosystem. Runoff from nearby agricultural areas introduces additional nutrients to the water and soil, occasionally causing imbalances in plant growth. When plant life becomes overly abundant, it disrupts the natural cycles of herbivores and predators in the park. These disruptions can create unpredictable changes in population sizes across the entire food web.

Efforts to understand these changes are ongoing, as ecologists monitor how each species responds to shifts in their environment. By tracking the population sizes of different organisms and observing their feeding patterns, scientists hope to predict how the food web may continue to change in the coming years. This information can inform conservation strategies that help protect the park’s biodiversity.

Questions

1. Based on the information provided, what might happen to the spruce grouse population if the growth of plants, seeds, and leaf litter decreases?

   • (1) The spruce grouse population would likely increase due to less competition.

   • (2) The spruce grouse population would likely decrease due to less food availability.

   • (3) The spruce grouse population would remain stable regardless of plant growth.

   • (4) The spruce grouse population would directly increase the weasel population.

2. In the food web, which two organisms would likely be most affected by a sharp decline in beetle populations?

   • (1) Spiders and spruce grouse

   • (2) Shrews and mice

   • (3) Weasels and red foxes

   • (4) Sunlight and plants

3. Which factor could serve as a limiting factor for the red fox population in this ecosystem?

   • (1) Temperature of the soil

   • (2) Availability of water sources

   • (3) Availability of herbivores like mice and grouse

   • (4) Amount of leaf litter

4. Explain one possible consequence on the food web if agricultural runoff continues to increase plant growth at a rapid rate.
   (Consider how excessive plant growth might affect herbivores and their predators.) [1]

5. If a disease reduced the population of mice significantly, how might this impact the ecosystem?

   • (1) Weasels and red foxes might have fewer food sources, causing a decline in their populations.

   • (2) Spruce grouse populations would increase because they consume mice.

   • (3) Shrews would increase as they rely on sunlight for energy.

   • (4) The food web would stabilize as other herbivores fill the gap.