(pleasant piano music) – [Narrator] California’s iconic sequoias are the largest trees on Earth. These giants have lived
for thousands of years, surviving war, famine and
the rise of globalization, but California’s ongoing
drought could mean disaster. These enormous trees are already
showing signs of weakness never seen before. Anthony Ambrose and a team of researchers are heading into the forest to climb hundreds of feet in the air and see what can be done to
save these magnificent trees. (dramatic music) – Our research entails climbing
the giant sequoia trees and measuring their water status, basically an index of
how stressed they are relative to the environment. The water status of all plants is kind of like the equivalent
of blood pressure in a human. It’s just a basic measure
of how much water they have available to them to
continue to function and grow so we clip little shoots of foliage and we put the little piece
of foliage leaf end down into this pressurized chamber and the amount of
pressure it takes to push the water back out of the stem is equal to the amount
of tension it was under when you cut that piece of foliage. When water availability declines,
such as during a drought, that creates a lot more
tension in the tree. When the tension becomes too great, then tiny little air
bubbles form in the wood and when it gets bad enough then the plant suffers and starts to die. (gentle piano music) There’s a couple reasons
why we need to climb to the tops of these trees. As water moves up the tree, it’s fighting gravity and friction and the top of the tree is gonna be the most stressed part of the tree. So, in order to get a really good idea of how stressed they are, we need to go to the very tippy top. It’s a real humbling experience because you’re up in the crown of these massive, ancient things and they make you feel small. I’m at the top of a very
large, giant sequoia tree waiting for the sunrise
’cause it’s really, really pretty this morning. It’s important to realize and remember that these trees have been
living for thousands of years and they’ve dealt with
pretty severe events, fires and droughts in the past, and they’re amazingly resilient. One of the things that
really is remarkable about these trees is their ability to recover from drought-type events. The question is, as conditions change, as temperatures continue
to increase globally, are conditions gonna change to a point where they may reach some threshold where they’re not able to recover from these type of events. (dramatic music) It’s an absolutely
amazing, unique experience to be able to climb into these trees. We want to preserve them. We want them to be here and we want them to be healthy and happy. (dinging)