Giant trees and what kills them is something
people have thought about.

But it’s something we haven’t really had
good data on, ever.

So while we know they’re really important,
they have these big effects,

we don’t know when, where or why giant trees die,
really anywhere, in the tropics,

which is a really important knowledge gap.

These trees are like the monuments of the forest.

For them to reach this size and to live for
so, so, so long, hundreds of years,

they had to survive a lot of things.

They are one of millions that
have managed to get to this size.

How many times has someone passed by this tree,

how many animals have passed by this tree

in these hundreds of years?

How many things have changed in our climate,
on our planet?

All the stories the forest has experienced.

There are three giant trees that have fallen

and it’s our laboratory under the open sky

So we arrived at the clearing and tried
to understand what caused it.

It certainly wasn’t a direct human action

but from the evidence we have,
we can see this tangle of branches from here.

A lot going on. In this case, it was this very
large tree that felled a couple of other trees.

65.0

Only giant, they are giant trees
from 50 centimeters [19.7 inches].

It’s 15-20 days since the tree fell.

This was a wind disturbance, because there
are some smaller trees also that are split

and also some of the leaves of
the trees that fell, that were uprooted.

They still have some green leaves and we also still
have wood that is very fresh.

So we know that this tree fell when it was still alive.

When it dies, the amount of nutrients it has here,
the amount of light

it releases will create a new beginning here.

That’s the map of Ducke.

This area of Ducke is 10 square kilometers [3.9 square miles]
and has this grid system here.

The drone is going to fly
1500 hectares [3,706 acres].

We change the scale to get a much better
understanding of the landscape,

usually a lot of area,
50 hectares [123 acres] at most.

I don’t think this technology replaces
going out into the field

and the knowledge we acquire by measuring
the trees, going into the clearings.

It’s just that this partnership between technology and field knowledge is fundamental for us

to be able to expand on what we already know.

Based on the patterns of damage, we think that there’s
a good chance this could be a lightning strike,

which is something we’ve been looking for for the last week so that we can do some training with the team.

So that when they see lightning strikes in the future,
they’ll be prepared to identify them.

There are lots of things that
can kill trees – droughts, wind.

When we get here and we see this tree broken, straight away,
we can think about wind as one of the causes.

But we have enough evidence that looking at the canopy to
tell us that this is probably lightning and not wind.

You can look at these trees that are here

and from the tree that would have been
directly struck by lightning,

the one that would have received all that current.

You sometimes can have many trees dead,
standing dead, together,

but not with this pattern of, like,
very centralized damage.

This sort of spiderwebs out through the canopy.

So it’s that directly struck tree and the one
next to it might be dead, too,

and then all of its neighbors have damage

and then some of those neighbors have damage
and propagates outwards.

And that’s how you go from not one tree damaged,
not two, but, you know, 20, 30, 40,

sometimes 120 trees damaged in a single lightning strike.

We’ve been having an increase in storm activity,

an increase in lightning strikes over the past several decades.

And there’s expectations that’s going to
increase into the future.

We know that’s happening, not just on its own, but with other events, too, with stronger droughts

all happening potentially in the same exact places.

So these forests aren’t experiencing one single problem,
one type of threat.

It’s all of these threats happening at once.

More lightning, more wind, more water stress.

They all seem to be occurring, and they’re all
of concern to the function of the forest.

We think we’ll be able to do necropsies
on around 1,000 trees at each site,

which is a fairly large number that will allow
us to calculate these mortality rates

and the cause of mortality for each
of these trees as well.

A forest like this that has these trees
that are the monuments of the forest.

It’s not going to be something you can
replace and rebuild very easily.

It has a huge importance for stabilizing
the planet’s climate

and for the climate we need to maintain
and mitigate climate change

but it also has this importance for the forest,
which is almost incalculable.

Once a giant tree like that has gone,
it will take hundreds of years for it to come back

and it’s a long time for all these biotic
interactions to take place and be rebuilt too.