Climate Change Lesson 10 : Ecosystem Relationships
Trying to predict specific long-term climate change impacts on ecosystems, places where biotic (living) organisms interact with abiotic (non-living) factors of the environment, remains difficult. However, the sensitivity of various ecosystems in Michigan can be predicted from studying the existing impacts of change on specific organisms.
Every organism needs certain conditions to thrive. For example, abiotic variables that are important for determining where individual terrestrial plant species survive include: pH, soil texture, soil moisture, soil depth, nutrient availability, air temperature, humidity, precipitation, sunlight, space, landscape features, and disturbances like wind, fire, and flooding. Important biotic variables include competitors for resources, herbivores, pollinators, seed dispersers, and fungal associates. Species with small and isolated ranges and quite specific biotic or abiotic needs are often the most susceptible to decline, disappearing locally, or extirpation, and even complete species extinction when faced with land use changes or other stresses.
Species with small or narrow ranges and/or those dependent on unique, fixed geologic features in Michigan will likely be the most susceptible to impacts from global warming. Warmer temperatures may shift further north, but the plants that grow in them may not be adapted to the different bedrock and soil features of northern Michigan. Furthermore, other community members necessary for the survival of the plants may not shift to the same location.
Some plants have evolved to require specific animals to pollinate them or disperse their seed. On the flip side, some animals require certain plants for food or cover. The loss of one of these species may result in the direct loss of the other. For example, larvae, or caterpillars, of the Karner blue butterfly (Lycaeides melissa samuelis) eat only wild or blue lupine (Lupinus perennis) leaves and flowers. Karner blues and lupine are found, along with many other rare and unique plant and animal species, in oak barrens (also called savannas), oak-pine barrens, dry sand prairies, and other open areas with sandy soil in Michigan. Although once ranging from Maine to Minnesota, the Karner blue butterfly has been reduced to small populations in Indiana, Michigan, Minnesota, New Hampshire, New York, and Wisconsin. These habitats are some of the rarest natural systems in the world, and if environmental conditions change and certain locations become unsuitable for wild and blue lupine, the Karner blue butterfly will also disappear from those sites.
Climate change will likely affect the relationship among biotic and abiotic factors in all of Michigan’s ecosystems. Depending on how each variable responds, ecosystems may shift locations but some special habitats and species may be lost.
The geographic range of a plant or animal species is an indication of its environmental “preferences,” the conditions that it finds ideal, acceptable, or intolerable. If the climate changes, therefore, it is reasonable to expect that plant and animal species might “move” to occupy different places. The big question is: “What species will move, and where will they go?”
The ecological habitat of a plant or animal species is the complete set of environmental conditions in the place where the species does well – normal temperature, temperature extremes, wind speed, moisture availability, soil quality, slope, insects, diseases, and so forth. Many of the minor terrain and soil features are not apparent on maps that show an entire state or country – on that kind of map, the broad gradients of temperature and precipitation appear to be the major controls on where a particular kind of plant can grow.
Note: As the specific climate changes and impacts remain difficult to predict, especially at a local level, this activity is not about teaching students exactly what will happen to Michigan’s ecosystems. Rather, the purpose of this activity is for students to understand the complexities and interconnectedness of ecosystems and then to think critically about what might happen to plants, animals, and ecosystems with changing climate. The students’ reasoning and discussion are the focus, not specific conclusions.