- Just ahead on "This American Land"... - The river smelled like garbage.

- What a transformation.

These dragonflies signal a new beginning for one Arizona river.

- It's a really beautiful place to be again.

- Lots of current, lots of fresh water.

- Keeping up with a growing appetite for seafood and the challenges of farming in our oceans.

An Indian community solves two environmental challenges with one elegant innovation.

- We're meeting the moment here.

- The moment has arrived for "This American Land."

[upbeat music] ♪ ♪ Funding for "This American Land" provided by the Walton Family Foundation, the Horner Family Fund, Roni and Jim Wilkins, Jr., Winchester, Virginia.

- Hello, and welcome to "This American Land."

I'm your host, Ed Arnett.

And on every show, you'll meet some of the dedicated professionals and volunteers working to tackle today's conservation challenges.

Today's show features some innovative ways of using sunlight and water.

Correspondent Brad Hicks takes us first to southern Arizona, where water from an unlikely source is helping save an entire ecosystem.

- Near Tucson, Arizona, Colton Shepherd is on the hunt... - Got 'em.

- For dragonflies and their smaller cousins, damselflies.

- Yeah, I caught three in one cast.

- Back when he was born, his net would have come up empty here, and his feet would have been wading through sewage.

The Santa Cruz River stands out as the only river that crosses the US-Mexico border twice.

It starts in south Arizona, does a 25-mile-long U-turn in New Mexico, then moves north through Nogales and Tucson.

For 4,000 years, it was the cradle of the oldest continuous agriculture in North America until Western expansion killed it.

- We sunk a whole bunch of wells.

The groundwater receded.

The river followed suit and went away.

And the river was left for dead.

- Then in the 1970s, a nail in the coffin-- three wastewater treatment plants were built along its banks, two in Tucson and one near Nogales.

The river was no longer dry.

It was filled with polluted water.

- It was almost insult to injury.

I don't think that there was much more nails that the coffin could take.

- People living near the river during that time never bothered to go there.

The smell kept them away.

- The river didn't feel safe.

It, you know, had garbage or smelled like garbage.

- But the wretched water also sent out a warning.

In 2005, downstream from the wastewater treatment plant near Nogales, an environmental calamity-- eight miles of cottonwood and willow trees along the river suddenly died.

- Even though these trees were inches away from the water, the poor water quality that was coming out of that wastewater treatment plant was causing the river bottom to clog.

So the water was flowing downstream, but it wasn't percolating into the ground where the trees' roots were, and it ultimately killed off a lot of trees.

- The plant near Nogales was quickly upgraded, so the water coming out was clean and capable of helping instead of harming the ecosystem.

80% of the discharge from that plant is wastewater that's piped in from Mexico.

- Well, the benefit is on both sides.

Mexico doesn't have to invest as much in the infrastructure to serve their population, and the United States receives wastewater that turns into treated water that contributes with improving the Santa Cruz River ecosystem.

[bright acoustic music] - And just a few years after the upgrades, something remarkable happened.

- An endangered fish returning to the river.

- Claire Zugmeyer, an ecologist with the Sonoran Institute, was there that day in 2015.

- It was near the start of our fish survey, and we hadn't yet set up to start the survey, and one of our partners had a dip net and saw some fish and just casually grabbed some and looked at them, and I think we have a topminnow.

- The Gila topminnow.

- Yeah, the Gila topminnow is great.

- The endangered native species hadn't been seen in the river in more than a century, and the little fish had a big message.

The river was coming back to life.

- This is the Agua Nueva Water Reclamation Facility.

- Seeing how improvements at the Nogales plant helped the river, the two plants in Tucson quickly followed with a $600 million upgrade.

- We are creating a river by operating our water reclamation facilities.

It's a really neat thing happening, and it's one that the community really cherishes.

- The wastewater treatment plants along the Santa Cruz now have brought back to life about 40 miles of the river.

The rest is still dry most of the year, but the parts that are perennial because of the treatment plants are sanctuaries for wildlife, plants, and people.

- Red-winged blackbird friend over there.

- Rebecca Perez grew up when the river was full of garbage and pollution.

- So what do you feel as you're here now and you see this river coming back to life?

- I feel a lot of hope for my son.

He's a year.

It has huge impacts on the well-being and health of the community physically, emotionally, mentally, spiritually.

It's so much more than some of the things that you can measure in ecology.

- The Santa Cruz story is such a success, the river is now even receiving water from the most unlikely source of all, a superfund site.

In the late 1980s, a chemical used in solvents was discovered in the groundwater around Tucson Airport.

The plume stretched for several miles and became a superfund cleanup site.

For decades, the water was treated here and put back into the potable water system.

- This is the advanced oxidation process.

- But just as the city was close to finishing the cleanup a few years ago, a curveball-- PFAS, forever chemicals were found in the water.

And while the treatment plant can remove them...

So the PFAS just gets absorbed by the carbon?

- It's just absorbed by the carbon.

- It was no longer considered suitable to drink.

- With PFAS entering the recovered groundwater, we ended up stopping that, and we came up with a different project.

We literally looked and went, we're 200 feet from the river.

Let's just get a pipeline to the river.

- I have a little male with pretty blue eyes.

- Which is another reason Colton can catch all the damselflies and dragonflies he wants.

- I like how they're all different species.

- He was netting them during a community dragonfly day along the river.

- So this is the way that we actually want to hold dragonflies when we get a hold of them.

- Before they surface and fly around for their final weeks of life to find a mate, dragonflies spend about seven months underwater as larvae.

- The diversity and the abundance of the dragonflies underwater tells us about the water quality.

So when we only see one or two species flying around, we think something pretty bad has happened with this water body.

But here today, we've probably seen, you know, at least 18 or 20 species already.

- The dragonflies have become ambassadors of the river, another reason for the community to come down and experience this natural wonder created by wastewater.

- Well, we're going to let them go.

OK. Bye.

- There she goes.

- This river is life, especially here in the Southwest.

Getting people connected with this water body is the foundational step towards continuing to restore this river and to get people excited about what its future could be.

- It's a really beautiful place to be again.

♪ ♪ - There's a huge and growing global demand for seafood, and that brings plenty of questions and challenges for the modern aquaculture industry.

Miles O'Brien from "PBS NewsHour" takes us to coastal Maine with a look at the sustainability of salmon farming.

- It was a perfect summer day when we steamed out of Southwest Harbor, Maine, on a different kind of fishing trip.

Is this a particularly good place to raise salmon?

- Certain places in Maine are ideal for salmon farming.

- Our guide was Andrew Lively with a Canadian company called Cooke Aquaculture.

- This is where these fish have been living for thousands of years.

This is an environment that they are well adapted to.

- And yet, pollution, dams, and fishing rendered Atlantic salmon an endangered species in the U.S. Cooke farms them at 120 leases here and in Canada.

The company raises all sorts of fish all over the planet, 18 countries in all.

Business is booming.

With wild fisheries maxed out and the global appetite for seafood rapidly increasing, aquaculture is now the fastest growing form of food production in the world.

- There's no question that there is a very good, strong demand for our product.

- Off of Swan's Island, we boarded the ship where they monitor and feed their crop of nearly a half million salmon.

They are kept in 16 flexible floating nets made with stainless steel fiber to guard against escapes.

We watched as they fed some of the fish using a network of submerged cameras.

- He's seeing the fish, and there's no feed coming down through the water column.

- The trick is releasing the feed at just the right rate.

Too fast, and it falls to the bottom of the sea, impacting the bottom line.

But it also can cause an environmental problem.

As the feed decomposes, it generates nitrogen, as does the fish poop.

High nitrogen levels are a persistent problem for salmon farmers.

- Do you feel like you've met those challenges?

- One of--the big way to deal with that challenge is proper site location and proper density.

We're in an area that gets about a 12-foot rise and fall of water twice a day, so lots of current, lots of fresh water going through here.

- Even at the perfect location, fish farmers must closely monitor a myriad of factors to keep their crops healthy.

Farmed salmon are frequently beset with serious infestations of sea lice.

To combat the problem, Cooke deploys custom-designed boats equipped with warm freshwater showers to clean the fish.

It's an expensive solution that might soon have an unlikely replacement.

- All right.

- Marine biologist Steve Eddy is director of the Center for Cooperative Aquaculture Research at the University of Maine.

These fish are lumpfish.

Tell me about them.

- So these are used as a cleaner fish to remove sea lice off of farmed salmon, a form of biological control.

- Norwegian salmon farmers, the pioneers and juggernauts of the industry, developed the technique.

Researchers here believe one or two lumpfish per 10 salmon in a pen should be enough to delouse the whole school.

- And then, as the salmon swim by and the sea lice start becoming a problem, they will dart out and pluck that sea louse right off of the salmon's back and eat it.

- Cooke makes its own feed.

It is a mix of plant and marine life, like these Peruvian anchovies.

The company claims each pound of salmon sold at market requires 6/10 of a pound of fishmeal and fish oil.

In the early days of the industry 30 years ago, it required almost seven times as much.

- These fish are six-month-old Atlantic salmon.

- OK. - So they... - Microbiologist Debbie Bouchard is director of the University of Maine Aquaculture Research Institute.

She and her team are looking at alternatives to make salmon aquaculture more sustainable, including insects.

- Fishmeal is more complicated than just the protein you're putting in it, as long as they're getting the omega 3s and the other fish oil and the other oils that they need, and we've come a long way in still having them taste really good like an Atlantic salmon.

- It takes about three years for a salmon to grow from egg to market.

As complex and resource-intensive as aquaculture is, its sustainability compares favorably to some land-based agriculture.

Author and journalist Paul Greenberg has spent much of his career focused on the fishing industry.

- We've already halved the feed inputs and doubled the growth rate, so that's pretty-- if you're a scientist, you're like, wow, that's amazing.

Could we go further?

So I can understand them being excited about that momentum, but then, you know, if you kind of stop drinking the Kool-Aid for a moment and look at the other options on the table, like things that are already extremely efficient, then you're sort of like, well, come on, let's just put it in perspective.

- The other options-- aquatic farms that produce crops further down the food chain.

And in fact, mussel and oyster farms here in Maine are also doing well.

These crops require no inputs, filter the water, and capture carbon, sustainable sources of protein for a planet on its way to a population of 9 billion.

- I think the oceans actually have a really important role in feeding both the present and the future of humanity.

- Between 70% and 85% of the seafood Americans eat is imported.

And the U.S. is 18th on the list of aquaculture producers.

With its long, sparsely populated coastline, Maine may be an ideal place for aquaculture to grow, but a coalition of lobster fishers and summer residents are opposed.

Jeri Bowers is a ninth-generation Mainer who lives near Frenchman Bay, where a company called American Aquafarms seeks to build a 120-acre salmon farm and hatchery.

- To see this proposal right here in the heart of Acadia National Park, really, I think, rang some alarm bells for all of us.

- The project is mired in opposition, but she says the state is too eager to approve aquaculture leases.

- It's the equivalent of, you know, setting up a farm on the town green.

That's really what it's like.

These are public waters.

And so while I'm really supportive of, you know, making a living on the water, I want it done in a balanced way.

- Jeri Bowers believes land-based aquaculture is a better idea.

That seeming contradiction in terms is gaining momentum as consumers demand, technology permits, and the oceans reach their limits.

♪ ♪ - Back on land, there's a growing cash crop that's harvested from 93 million miles away.

Sunshine and solar panels are helping families keep up with the constant demands of running a farm.

Let's go to Minnesota, where the sun's rays have joined soybeans and hay to boost the bottom line.

[gentle music] ♪ ♪ - My father purchased this farm in 1960, and I bought it from him in the early '90s.

[truck rumbling, hissing] We grow corn, soybeans, and some hay.

This is soybeans we're loading here.

And, of course, we use electric power.

The electric motor drives the unload auger that's in the bottom of the bin.

And then when we're about empty, we throw a sweep in, and that brings them to the center and out the bottom.

That's what we use electricity for, for the grain site.

Thank you.

My name is Roger Walkes, and I farm in Plainview, Minnesota.

♪ ♪ This is where our biggest power is used on the farm anymore, in the fall, when we're harvesting and drying grain.

We dry the grain temperature of anywhere from 150 up to 180.

We have motors on every auger and cooling fans on the bin, and we still have stock water heaters in the winter.

They take a lot of juice, and then just basically for our needs here in the house and stuff for heat, air conditioning.

This little machine here does all my calculating.

There's a lot of challenges on the farm, and the biggest thing is probably finances anymore.

Our prices are way out of whack compared to the cost of production and so many variables.

We fight the weather.

And it's kind of a battle, and you've got to be able to look for solutions and carry on.

♪ ♪ One of the challenges that we can control is I went with this solar project-- always going to need electricity, and the cost of electricity is not going to go down, I'm sure.

- What we're looking at here-- 33.66 KW ground-mounted solar array, consists of 102 330-watt panels.

My name is Chris Olofson, and I work for Solar Connection in Rochester, Minnesota.

The biggest thing for Roger is that him and his wife, Judy, have consistently seen their electric bills go up over those years.

And so when I first met with them, the first question that Roger had to ask was, how big can I go to cover what I need?

- I was reading about it, and I'd see the incentives that would save me some money and possibly some grants and stuff.

This is a good thing to have in-between them.

It helps keep the weeds down, and good for the bees, too-- pollinators.

- The federal income tax credit is still around.

So there are still very good incentives that are available for everyone.

This is a grid-tied solar array.

If there's more solar being produced than the house is consuming, that power then gets sold back to the utility.

- Full sun, and it just really puts out.

- Here in Minnesota, we have a very good policy at the state level called net metering that requires all utilities to pay you at the same rate for the energy you sell as what they're charging you.

It looks like they've put out about 38,000 kilowatt hours so far.

So they're ahead of schedule.

And in his case, he didn't want to sell a lot of the energy back.

He just wanted to offset his consumption.

- Should provide all our power and about 20% extra.

- There is a momentum across the state.

It has more to do with people's ideals, meeting their finances, where clean energy keeps coming down in cost.

It's really cost-effective to do.

And, you know, he's doing good by the environment as well.

- My name is Fritz Ebinger.

I work for the Clean Energy Resource Team for the University of Minnesota Extension.

Back in 2013, the state passed a 1.5% solar energy standard, which was a mandate.

Part of that legislation involved a 10% solar energy goal by the year 2030.

We already satisfied the 1.5% mandate a while ago, just because the cost effectiveness of solar is so good.

So it's still a goal.

[bright acoustic music] ♪ ♪ We've seen a lot of utility companies pivot towards renewable energy as a cost-effective generation.

And you figure out how to create probably a greener mix between natural gas, solar, and large-scale wind.

If you look at the statistics, farmers are getting a little bit larger, and smaller farmers are trying to figure out how to make their way through.

One of the ways to do that is to expand, basically acquire more land or maybe more livestock.

Another way is to specialize, and then diversification, which would include solar now.

So farmers that can host a small amount of solar-- that's another revenue stream for them.

Utilities scale solar development, whether that's a 1 megawatt community solar garden or maybe a piece of a larger development, does present, like, a mitigating benefit financially.

You're reducing your inputs 'cause you're not tilling and planting in that area anymore, and then you're also getting a lot more lease money than you would otherwise from marginal land.

- Being a farmer, it probably makes more sense than somebody in town that might sell in a couple of years or move on to another job or something.

But the farm generally stays, you know, a lot of times in the family.

♪ ♪ - Growing up, I started doing chores.

I think I was about four.

I have several memories of falling asleep in the parlor, watching them milk.

I think I was supposed to go to bed, but I decided to play around some more.

I am Rachel Walkes.

I work here at Mayo Clinic, and I am the daughter of Roger Walkes.

Oh, yes, I named the cows.

I did it in alphabetical order so that I could easily know which one was born in which order.

Qs, Ys, and Zs were not my friends.

We might have used Yak several times.

The most compelling reason to me to move forward with our solar project-- growing up, we started doing 100% no till on our farm.

So not only were we trying to conserve water and soil, the next thing, why not try to conserve energy?

Whether it be wind or solar, I was on board.

So I think this is a great opportunity to make this investment so that as I eventually get to take over the family farm, that I'm able to use these funds that we're saving from the energy bill and go ahead and spend that other places where I can invest and improve the farm.

- Power costs are always going to continue to rise, and the sun is free.

You might as well be self-sufficient with your power.

- I think farmers really are forward thinkers, and they understand how technology works.

And they certainly are stewards of the environment, and this is just another example of how you can be both a steward financially and environmentally.

- I think we're making a positive impact on the planet, just because we are setting an example for others to try to see how they can either reduce, generate, do something to make a change so maybe we have less of a footprint, leaving things better off than what we found them.

[bright acoustic music] - In the desert Southwest, one Indigenous community is combining innovations in both solar and water technology for a historic first.

Brad Hicks shows us how these pioneers are drawing on their past for inspiration.

- With the flip of a switch, a new source started sending power to the grid.

This stretch of solar panels south of Phoenix may not seem special, but what's under this canopy could impact how Western communities adapt to warming temperatures and drier weather.

- We're meeting the moment here.

- The innovators are Indigenous, the Gila River Indian community.

They've built this canopy of solar panels over an irrigation canal.

- This has never been done in North America before, never been done in the Western hemisphere.

So this could be a new paradigm for irrigation in the Western United States.

- The panels produce power, but equally important, they prevent evaporation, a huge problem here in the desert.

The shade they create could also keep algae from growing in the canal, cutting maintenance costs.

And the cooling effect of the water under the panels should make them more efficient.

- For the world to see that a tribal nation can do this, we're at the forefront of this.

We're at the cutting edge, you know, of finding ways to address climate change.

- Right now, just over a half mile of this canal is covered, but when the 16-mile-long canal is complete, it could supply half the energy needs of the entire community and save enormous amounts of water for irrigation.

- Community's vision is to establish the first and only in the world completely carbon-neutral irrigation district, meaning that whatever its power demand is, we will generate through renewable energy.

- The Indigenous people here are considered one of the most successful canal-building cultures in human history, dating back 2,000 years.

By harnessing solar to save water, they are taking their canal-building heritage to new heights.

- And this links so beautifully to our traditions.

If this moment becomes a movement, we're going to look back and just see that this is a historic time in how we address and adapt to our changing environment.

♪ ♪ - Now here's a look at stories coming up on our next show.

- Ruffed grouse numbers have been on a steady decline.

Find out how improving forest habitats can help them recover.

- Today, we're going to put a studio-quality microphone out there with the peregrine falcons.

- And witness some mic-drop moments with these raptor reality stars.

- Thanks for watching.

We'll see you next time on "This American Land."

- And you can always watch our show on PBS Passport.

Funding for "This American Land" provided by the Walton Family Foundation, the Horner Family Fund, Roni and Jim Wilkins, Jr., Winchester, Virginia.