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[rythmic music begins]  Narrator:
The White House recently called upon the USDA's

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Forest Service and the Bureau of Land
Management to produce the first ever

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national inventory of mature
and old growth forests.

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After a year’s work,
the first stage is complete,

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and thanks to observations
from high above, scientists will soon

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be able to view, measure and understand
our forests like never before.

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NASA's GEDI instrument on board
the International Space Station

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helps estimate tree height and biomass,

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adding a new dimension to the study.

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Palmer: The Forest Service has been studying

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old growth forests going back
almost 100 years.

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Others before us have been studying
in much longer.

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Many of these forests have been managed

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for millennia by native peoples who have
deep connections to these forests.

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But we still have a tremendous amount
to learn.

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We have data
that's been measured on the ground

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that tells us a tremendous amount
about what's out there.

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But a ground inventory is necessarily
going to have gaps in it.

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We can measure one plot
for every 6000 acres of forest.

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What remote sensing data does
is it really allows us

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to fill in those spatial gaps,
but also the temporal gaps.

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We know that
with the frequency of disturbances

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that are happening on our landscape now,
we need more rapid information.

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So, for example, with the
NASA GEDI sensor that we're using in this

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particular study,
we're working with the NASA scientists

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to identify that relationship
with those ground-measured

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information we know about forests.

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Narrator: Ground surveys collect
detailed information about forest types

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and health, and tree ring data,
provide a window back in time.

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Pederson: Today, we're in a

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marginally documented old growth forest.

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It's on Forest Service land
in the Tionesta National Forest.

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And this is home to the oldest
documented eastern hemlock.

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And we're putting in plot today
and then going to try to core

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some more older trees
so we can get about five to

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maybe six centuries of history.

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Looks like it's got a density of rings
and a release.

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Old growth forests are quite often
where we go

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to get those long histories
where we can learn about

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frost events
and droughts and insect outbreaks

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and any kind of important ecological,
climatological, and even sometimes

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cultural events that happen, 
they’re stored in the trunks of these trees.

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And the oldest trees have the best stories
because they can go farther

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back in time.

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Narrator: These living

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time capsules and their ecosystems
help clean our air and drinking water

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and provide spaces
for recreation and wildlife.

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They also help absorb
more than 10% of our annual greenhouse

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gas emissions. While younger vegetation
accumulates carbon more rapidly,

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old growth forests contain more biomass
overall and store more carbon,

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another variable
that can be estimated from space.

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In addition to GEDI, observations
from NASA's ICESat-2 satellite

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and several field campaigns, have helped
measure our ever changing forests.

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Pederson: You know the precision of lidar

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now from a space station,
how you can beam the lidar

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system down
and in 30 meter radius plots.

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you can pull in all this information
about the height of the canopy,

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the changes in the canopy over space,
and density of the forest.

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The precision of these beams
now from outer space

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to get detailed information about a forest

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is truly astounding.

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These ecosystems are so complex.

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From the treetop to the bedrock. Right?

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We're still learning so much about
what's underground, what's in the soil,

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this live dynamic system
and what we can't see.

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The old growth forests have a function
of time that as a human, we can't fathom.

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From a Western science perspective,
we do not understand.

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And it wouldn't be
wise to lose these systems.