[rythmic music begins] Narrator: The White House recently called upon the USDA's
Forest Service and the Bureau of Land Management to produce the first ever
national inventory of mature and old growth forests.
After a year’s work, the first stage is complete,
and thanks to observations from high above, scientists will soon
be able to view, measure and understand our forests like never before.
NASA's GEDI instrument on board the International Space Station
helps estimate tree height and biomass,
adding a new dimension to the study.
Palmer: The Forest Service has been studying
old growth forests going back almost 100 years.
Others before us have been studying in much longer.
Many of these forests have been managed
for millennia by native peoples who have deep connections to these forests.
But we still have a tremendous amount to learn.
We have data that's been measured on the ground
that tells us a tremendous amount about what's out there.
But a ground inventory is necessarily going to have gaps in it.
We can measure one plot for every 6000 acres of forest.
What remote sensing data does is it really allows us
to fill in those spatial gaps, but also the temporal gaps.
We know that with the frequency of disturbances
that are happening on our landscape now, we need more rapid information.
So, for example, with the NASA GEDI sensor that we're using in this
particular study, we're working with the NASA scientists
to identify that relationship with those ground-measured
information we know about forests.
Narrator: Ground surveys collect detailed information about forest types
and health, and tree ring data, provide a window back in time.
Pederson: Today, we're in a
marginally documented old growth forest.
It's on Forest Service land in the Tionesta National Forest.
And this is home to the oldest documented eastern hemlock.
And we're putting in plot today and then going to try to core
some more older trees so we can get about five to
maybe six centuries of history.
Looks like it's got a density of rings and a release.
Old growth forests are quite often where we go
to get those long histories where we can learn about
frost events and droughts and insect outbreaks
and any kind of important ecological, climatological, and even sometimes
cultural events that happen, they’re stored in the trunks of these trees.
And the oldest trees have the best stories because they can go farther
back in time.
Narrator: These living
time capsules and their ecosystems help clean our air and drinking water
and provide spaces for recreation and wildlife.
They also help absorb more than 10% of our annual greenhouse
gas emissions. While younger vegetation accumulates carbon more rapidly,
old growth forests contain more biomass overall and store more carbon,
another variable that can be estimated from space.
In addition to GEDI, observations from NASA's ICESat-2 satellite
and several field campaigns, have helped measure our ever changing forests.
Pederson: You know the precision of lidar
now from a space station, how you can beam the lidar
system down and in 30 meter radius plots.
you can pull in all this information about the height of the canopy,
the changes in the canopy over space, and density of the forest.
The precision of these beams now from outer space
to get detailed information about a forest
is truly astounding.
These ecosystems are so complex.
From the treetop to the bedrock. Right?
We're still learning so much about what's underground, what's in the soil,
this live dynamic system and what we can't see.
The old growth forests have a function of time that as a human, we can't fathom.
From a Western science perspective, we do not understand.
And it wouldn't be wise to lose these systems.