Why we need to move trees
The redwoods of America’s Western coast are one of the world’s largest tree species. They inhabit a narrow strip of land near mountains and valleys where a combination of rain and fog provides them with the water they need to grow. Over time, changes to the climate can alter the amount of rain and fog in the redwood habitat. One way trees have dealt with this in the past is by slowly migrating towards areas with better climate.
Let’s visualize this migration below, on the left is a map of the redwood habitat. indicates where trees are, indicates land where they could grow, and indicates where they can’t grow - on water for example.
On the right is a map of the climate in this same habitat. Lighter indicates a dry climate, darker indicates a wet one.
Press play to watch the redwoods migrate from the bottom which is slowly drying out, to the top where it remains wetter.
In modern times, these climate shifts are happening much faster. Redwoods migrate slowly because their cones can only travel a short distance each generation. With the drying happening faster than before, the redwoods are unable to reach the wet habitat at the top of the map, and disappear from the land that is now too dry for them.
One way of combating this problem is by planting redwoods in suitable areas where they haven’t yet reached. This speeds up the migration and prevents them from disappearing altogether. You can save the redwoods yourself by clicking at the top of the map to plant new trees. To try again, click reset.
Of course reality is not this simple, scientists need to carefully survey areas where the redwoods can grow well before planting them. Caution needs to be exercised so that introducing the new species doesn’t hurt the environment that’s already there.
This process is called “assisted migration”. It’s one tool that can be used to deal with our environmental problems, not just for redwoods but for many tree species. If you want to explore this further, use the sandbox below. Click on the coloured squares and drag on the map to draw your own habitat and climate. The numbers let you decide how fast the climate is drying.