♪♪ Sunrise over this peaceful orchard.

Sheep contentedly graze nearby.

Quiet for now, but things are about to go... nuts!

[Loud machinery noises] Welcome to Sierra Orchards, near the northern California town of Winters.

Craig McNamara, his family, and their longtime workers have been harvesting walnuts on this 350 acre farm for more than 40 years.

California farms nearly a half million acres of walnuts and produces 99% of all the walnuts grown in the U.S., about 750,000 tons each year.

[Craig McNamara] This is a beautiful tree, if you look at the structure of it.

Each family member's ag journey is unique.

Julie got her first taste of agriculture on a dairy farm in New York's Hudson Valley.

Her love of organic farming led her to a long career in the ag department at UC Davis.

[Julie] It's just what spoke to me, what resonated with me.

I think it is a precious, precious commodity that needs to be preserved and respected and... and cherished.

After dropping out of college, Craig says he worked alongside and was inspired by subsistence farmers in Mexico, Peru, Ecuador and other places.

[Craig] And they taught me, really, the purpose of life.

They taught me how to survive, how important food is.

And I realized I wanted to be a farmer, to grow something that's nutritious, healthy, that I can get to people to improve their lives.

Like so many other families, Emily and Sean explored many other career paths before returning to the farm.

Both were inspired by their parents' deep commitment to sustainable, also known as regenerative, agriculture.

[Emily] I was able to realize how, um, special of a place my parents have created and, uh, how unique and cutting-edge some of the practices they were implementing were, and have been.

[Sean] I wouldn't want to farm any other way, but a lot of my farming decisions, uh, and inspiration are honestly born just in the desire to survive in this place.

[Craig] The future is one of resilience, and that's what we're trying to practice here on our farm.

So, resilience, to us, uh, is your sustainable agriculture, and really, the... the crux of it is soil health.

That commitment to sustainability and soil health happens throughout the year.

During the summer, the farm's 200 plus sheep graze in the orchard, keeping weeds under control so no herbicides are needed.

They're followed by chickens who eat bug pests and, like the sheep, leave manure.

That acts as fertilizer, though the animals are removed several months before the harvest to ensure food safety.

Cover crops are also planted to capture carbon from the atmosphere and return healthy nitrogen to the soil.

Harvest time brings a flurry of activity.

First, a powerful shaker jostles each tree, bringing thousands of walnuts to the ground.

They're swept to the center of each row, then harvested.

The nuts are loaded into double trailers called "nut buggies" and taken for processing.

Here, sticks and other debris are removed, then the nuts get a first washing.

Then, the hulls are removed, the nuts are washed again, human sorters make sure the remaining nuts are perfect and they're off to the driers.

[Craig] So, we use propane forced air, 110 degrees, dry the walnut.

It's looking beautiful at that point.

We convey all those walnuts, through elevators, up into clean sets of double trailers.

Big trucks come and take that to the processor.

But that's not the end of the story and the hard work.

All the harvest debris- hulls, bad walnuts, water used in processing, even walnut trees past their productive lives- are allowed to decompose here for a couple of months.

[Craig] In the spring and summer, we'll load it with a... with a front-end loader into our spreader and we'll just spread it out on the orchard floor as compost.

So, it's a... a wonderful recycling of what used to be farm waste.

All the McNamaras agree the years ahead will bring new and increasing challenges.

Already, summers here are hotter and winters, often, too mild.

That can lead to smaller yields and unpredictable prices.

Craig and Julie say they're both grateful and concerned their kids are joining them as they face the future.

[Craig] I want our children's lives to be connected to this land and as enjoyable as possible.

[Emily] I don't know what it will look like, but I see just new opportunities to really become creative so we can continue farming for generations to come.

[Sean] Every year, every season is an opportunity to learn.

So, I'm excited about the accumulation of knowledge that's happening here.

[Julie] I think there is a lot of promise.

They just have to be creative.

And I think they are creative and they've got the energy, so I'm hopeful.

♪♪ Walnuts have a rich history dating back thousands of years.

Walnuts are the oldest tree food known to man, dating back to 7000 B.C..

The Romans called walnuts Jupiter's Royal Acorn.

Early history indicates that English walnuts came from ancient Persia, where they were reserved for royalty.

Thus, the walnut is often known as the Persian Walnut.