Will Global Warming Push Trees to Extinction?

Scientists estimate that the earth's average temperature will rise by 2°F to 10°F in the next 100 years. The United States Environmental Protection Agency estimates that if the average temperature in the US rises by 3.6°F the climate in an area will shift north by about 300 kilometers or 200 miles. That is about 3 kilometers or 2 miles every year. If the temperature rises by 7°F the shift could be closer to 4 miles every year.

Birds and deer may be able to move north each year to stay in the climate range they prefer. Turtles, salamanders and plants may find this annual march more difficult or impossible.

Plants and animals that live in mountains have 2 options. They can move north or higher in elevation. The temperature drops about 3.5°F for each increase of 1000 feet in elevation. Some trees, like hemlock, prefer northern slopes. They grow in pockets scattered through the mountain range. The next site north that they can live on may be several miles away.

Unlike animals, plants can't walk or fly to find a new home. As the climate in a forest changes some kinds of trees will die. This may reduce the diversity of trees in the forest. Other trees from the south may now be able to survive in the forest. How can these new species move into the forest?

Trees move as seeds. Some seeds are blown by the wind. Maple, sycamore, and cotton wood trees are common examples of trees whose seeds are carried by the wind. Birds carry some seeds. Mulberry, magnolia, and holly are examples of trees that produce fruit that birds eat. The seeds are planted with the bird's droppings. Mammals like squirrels carry nuts. Oak, hickory, and walnut trees are examples of trees whose seeds are moved and buried by squirrels.

Seeds that are blown by the wind don't move very far. Some days the wind is gentle and the seeds may come to rest under the tree. On a windy day the seeds may be blown a few hundred feet. The distribution is a tenth of a mile or less.

Seeds that are moved by mammals are also moved short distances. Small mammals like squirrels have a small territory perhaps an acre or two. The squirrel buries the nut as a winter food source. The squirrel buries the nuts within a few hundred feet of the tree it fell from. 20,000 years ago there were large mammals, buffalo and mammoths that ate the nuts. A few days and miles away a few of these nuts were planted with the animals droppings. These large mammals aren't available to disperse the seed today.

Birds move some seeds. Small birds like finches and sparrows have a small territory, perhaps only a few acres. Other birds like crows or starlings, which travel in flocks, can cover several miles everyday. Birds like the cedar wax wing will stop and eat a small fruit while migrating north and south each year. These seeds are then dispersed 50 miles or more from the tree.

Some plants like dandelions may produce seeds in the spring. These seeds then grow into plants that produce more seeds later in the summer or fall. These quick growing plants can produce more than one generation each year. Trees have a longer life cycle. Most trees spend several years as saplings before they flower and produce their first seeds. Red and white pine trees can produce seeds after 2 years. White oak trees can take up to 50 years before they produce their first seeds.

Tree species live in an area or range. Some rare trees live within 20 or 50 miles of each other. For example McDonald Oak only live on the Channel Islands of California. Other tree species are spread across hundreds or even thousands of miles. For example White Oaks live from the Gulf of Mexico to Canada and Iowa to the Atlantic Ocean.

What will happen if the range for the White Oak moves north by 200 or 300 miles?

What will happen if the range for the McDonald Oak moves north by 200 or 300 miles?

The model in this lesson will help you explore how global warming will effect the trees in your state. You will determine which trees need help so they don't become endangered or extinct.

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