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What should we do about the trees?

Air temperatures are increasing in northern latitudes which is influencing where some trees and bugs are found. What will that mean for the northern forests over time?

1) Looking at the environment and the biology in the Arctic

Welcome to the world of trees! Here is a map of all the forests and trees globally in 2015.

terraPulse is compiling millions of satellite images of map forests around the world and how they’re changing over time. Explore your neighborhood and your planet! See how much can change in 10 years! (Check out the data maps on terraPulse to learn more about what they do)

Zoom in and out. Enter a location to look at more closely. Play around and see where there are and are not trees throughout the world.

There are some surprising aspects of this global forest map, like trees living really far north! Let’s explore that a little more.

2) Trees in the far north.

At 61.2°N Anchorage, AK is above the 60°N latitude definition of the northern polar region. However, it is not all ice and snow!

In fact that are a wide range of tree species, including tall ones, that grow and thrive around Anchorage. These trees are comfortable in cold air temperatures and do not need much sunlight (which is good as it is very dark in the winter months).

But the number of trees is not constant in Alaska over time. Also, what is happening to the trees as the air temperature has been warming over the past many decades?

Let’s find out!

3) Human caused changes in trees over time

There are human-caused and natural-caused reasons for changes in vegetation around Anchorage, AK over time.

First, let’s think about the human-caused reasons. For example, some common reasons why we clear trees are to harvest the timber to make wood products or to make room for other things that we want to do with the land (like build homes, grow food, etc.).

This can easily be seen by looking for large areas of trees (vegetation) that have been removed, most often in shapes with straight lines, like the image on the right.

Let’s see what this looks like in the data maps.

4) Reading human changes in the tree data

We can use satellites to look at changes in trees (tree canopy cover more specifically) over time through the terraPulse datasets (top image) or to see what the lack of trees looks like now (bottom image).

So, in the image from terraPulse the green represents… you got it, trees. The red represents where there used to be trees but there are no longer (specifically where trees were lost between 2010 and 2015).

Where do you see red in the data? What kind of shapes are the red patches? Do you think those red patches of tree loss are human-caused? Why or why not?

But we are not the only things that remove trees.

5) Natural causes for changes in trees

There are also natural, or non-human, causes for trees coming down around Alaska.

For example, the Spruce Bark Beetle likes to eat white, Lutz, and Sitka spruce trees, but usually not other trees. This beetle has been doing its own work at taking down trees throughout southern Alaska over the years.

We can look at the area (in acres) infested by the Spruce Bark Beetle around Anchorage, AK from 1990-2017. What do you notice in the data? As a note, 1,000 thousand acres is larger than the state of Rhode Island!

The beetles eat the tree (phloem cells) which kills the trees because they are eating the trees food. The trees die within a few weeks, but it can take up to a year for the needles to turn brown. Dead trees can be a falling and fire hazard.

So let’s dive into some more tree data from the satellites to see what this looks like!

6) Reading natural changes in the tree data

We can use the satellite data from terraPulse to look for patterns of spruce bark beetle kills of trees around Anchorage, AK. Here we are looking at an image of tree canopy cover from an area northwest of Anchorage.

Where do you see red in the data? What kind of shapes are the red patches? Do you think those red patches of tree loss are caused by beetles? Why or why not?

So what does this all mean for protecting forests around Alaska? Let’s dive into a hypothetical scenario around Anchorage, AK to see how we can use the data provided by terraPulse to make our decisions.

7) What should we do?

You are a park manager for the two city parks in Anchorage, AK. You have been watching the summer air temperatures rise over the past few summers and have heard of increased numbers of Spruce Bark Beetles killing trees around your area.

It is time to rethink the plan for how to best protect the trees, and people who visit the parks, in the future.

Use these data to get a sense of tree coverage and loss around Anchorage, AK and in the two parks (toggle the park outlines on and off to see where they are).

8) Decision time

Here are the options that your boss has presented for you to choose:

  • Keep all of the spruce trees, as it does not seem like we need to worry about beetles killing our trees.
  • Remove the old and slow-growing spruce trees, but keep all the rest.
  • Remove all of the spruce trees to ensure that none of them die and fall on people.

Keep exploring these satellite data and the previouslly provided resources on beetle kill as you make your decision.

What are you going to choose?

9) Check out your area

Choices about what to do with trees are not only happening in Anchorage, AK around Spruce Bark Beetles. All over the world people are making decisions each day using data such as these.

Drag the map around, or enter a specific location, to find your local area. What kinds of trees are there now? How much has it changed since 2010?

What about comparing Seattle, WA with Phoenix, AZ?

Or, compare New York, NY with Miami, FL.

Have fun exploring what we can learn from trees around the world!


Dr. Joseph O Sexton (Science Advisor)

Dr. Min Feng (Forest data developer)

University of Maryland Department of Geographical Sciences

terraPulse, Inc.

NASA Earth Sciences Division (Research Funding)

US Geological Survey (Satellite data)

Kristin Hunter-Thomson (Story Design)

Lucas Marxen (Interface Development)

Dan Farnsworth (Data Visualization & Website Development)

Photo Credit: Luke Jones
Photo Credit: Sam Beebe
Photo Credit: Giant Ginkgo
Photo Credit: Juan de Vojníkov
Photo Credit: CC BY-SA 3.0

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Taking Down Trees

Interested in learning more about Spruce Bark Beetles and how they are killing forests throughout Alaska? Check out these resources: