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Geese as Gardeners

Essential Question: What would happen to the plant communities if the geese went somewhere else?

Phenomenon: If geese disappeared, the coastal tundra would have different plant communities and it would look different. 

How does goose grazing affect the type of plants found in a coastal marsh? What would happen to the plant communities if the geese went somewhere else?


  • Define the term keystone species
  • Identify organisms that eat grass and sedge in the costal wetlands
  • Explain how geese affect their environment through grazing


  • grazing
  • keystone species
  • Hoppner”s Sedge (Carex subspathacea)
  • Willow (Salix ovalifolia)
  • herbivory (herbivorous)

Keystone Species

A keystone species is a species that has a disproportionately large effect on its environment relative to its abundance. Removing a keystone species from an area can cause major changes to the habitat and affect other organisms.

Are geese a keystone species?


Would this place look the same, if the geese no longer came here?

Goose Grazing

The Pacific Black Brant grazes on a coastal marsh plant called Carex subspathacea. Because they eat plants, they are herbivorous, or herbivores.  The common name for this plant is Hoppner’s Sedge. There are so many geese in the marsh that the sedge is always mowed (chopped) down by the geese. If the geese stopped cutting this grass back, other types of plants would begin to grow. In the coastal marshes of western Alaska, taller grasses that geese don’t eat and plants such as oval-leafed willow (Salix ovalifolia) might increase. What type of animals like to eat grass? If Willow plants started to dominate this area, what other animal might prefer this habitat?

Moose prefer willow plants that might compete with sedges for space. Geese prefer the sedges. Which animal is more important?

Researchers working on the Goose Project are collecting scientific data to understand how geese play an important role in creating a coastal marsh dominated by Hoppner’s sedge. Scientists at Tutokoke Camp near Chevak, Alaska are designing experiments to help answer these questions.

Geese also act as fertilizers to growing plants. As the eat, they poop and squish their poop into the ground. This adds nitrogen back into the soil and makes the plants growing faster and thicker.

To understand more about how geese influence the growth of grass, complete the Goose and Grass experiment described in the student activity handout.


  • A keystone species is an organism that has a large impact on it’s ecosystem. If this species is removed from the area it would impact the lives of many other plants and animals.
  • The sedge and plants in a coastal marsh grow quickly and provide food for shorebirds, geese, voles, mice, hawks, owls, fish, invertebrates and many other species.
  • By keeping the grass short, it stimulates the grass to grow in thicker and more quickly. This allows the grass to outcompete other plants. It there was no grazing the grass would grow taller and other plants could compete better for space.


  1. What is a keystone species
  2. How could geese considered a keystone species in the coastal wetlands of Alaska?

Explore More
The following videos give a good explanation of what a keystone species is. Watch each and answer the following questions:

  1. How are sea otter’s a keystone Species?
  2. What would happen if the sea otters disappeared?