A Wilderness Island Enrichment LESSON 1 Chapter 22

Name
Date
Class
Chapter 22
Enrichment
LESSON 1
A Wilderness Island
In the northwest part of Lake Superior,
is Isle Royale, a pristine island wilderness
and national park. Isle Royale consists of
one large island surrounded by about 400
smaller islands. In 1981, it was designated
a biosphere reserve, and it is part of a
program designed to protect examples of
the different ecosystems of the world and
to encourage research. It represents the
northern lake forest biome, part of the
taiga.
Biotic and Abiotic Factors
Ecological Relationships
Because of its isolation, relatively few
species have colonized Isle Royale. Moose
came to the island in the early 1900s.
Almost 75 percent of their diet consists of
balsam fir; they also eat lichens, twigs of
woody trees, shrubs, and aquatic plants.
Because the moose had no natural
predators on the island when they arrived,
their population grew rapidly until there
was not enough food to go around. With
nothing left to eat, the population crashed.
Over time, the plants that had sustained
the moose slowly began to grow back.
As the few remaining moose found more
and more food, they began to reproduce
rapidly, and the cycle started again.
In the winter of 1948–1949, a pack of
timber wolves crossed the ice of Lake
Superior to Isle Royale. Wolves are natural
predators of moose, and the relationship
between these two species is very complex.
The interactions among wolves, moose,
and the island’s vegetation have been the
subject of pioneering wildlife research for
more than 45 years.
Applying Critical-Thinking Skills
Directions: Respond to each statement.
1. Sugar maple and yellow birch trees are usually associated with the temperate deciduous
forest biome. Hypothesize why they are growing on Isle Royale, which is in the
northern lake forest/taiga biome.
2. Predict the effect that the arrival of wolves had on the cycle of moose on the island.
20
Biomes and Ecosystems
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Approximately 11,000 years ago, 3 km
of ice lay on Isle Royale, pressing it down
into the earth and sculpting its topography
of rocky cliffs, jagged coastline, and inland
lakes, ponds, and bogs.
The vegetation of the island is primarily
forests, and they are in transition. Aspen
and white birch that followed forest fires
caused by early settlers are declining
rapidly because of lack of fire. Northern
forests of balsam fir, white spruce, and
white birch occur near Lake Superior and
along some interior lakes where it is moist
and cool. On warmer and higher ridges,
sugar maple and yellow birch predominate.
Isle Royale is considered to be one of
the most intact ecosystems in the state of
Michigan due to its isolation and lack of
human influence. The island is accessible
only in summer and can be reached only
by boat or seaplane; wheeled vehicles are
not permitted.