Michael Aranda: Spring is in the air in the Northern Hemisphere, which means our world is about to become a whole lot greener.  If you're a gardener, it's time to break out that trowel.  And hundreds of billions of farmers are gearing up to cultivate this year's harvest.  So we thought it was a good time to talk about the science of growing things, from the tomatoes in your garden, to big scary corporate agriculture companies.  We'll start small and right at home.

Gardening can be a lot of work, and when you add the cost of fertilizer in, it can be downright expensive. If you're looking for ways to cut costs, you might be tempted to make your own by essentially recycling your leftovers as compost. But you might be annoyed that you can't compost everything. Meats and dairy are generally a no-go. That's not actually because you can't compost them though. Here's Hank with the science of composting meat.

Hank: If you have a composting service at your work or school, you might have noticed an odd pattern. They can take as many apple cores and paper towels as you care to give them, but they will not accept meat or dairy. And if you compost at home, you might also avoid adding those things to your pile. But the problem isn't that it's hard to break those things down, the problem is that it's easy - too easy.

Composting is a way to convert things like food scraps and yard trimmings into fertilizer, instead of sending those things to landfills. So it might seem annoying that you can't toss all your leftovers in, and it turns out you can - if you're careful. 

Some of the problems with composting meat are practical. It can attract pests, and you probably don't want to have to fight off a bunch of rats and raccoons in your backyard, plus some folks worry about disease-causing bacteria being able to grow in home compost piles. But the solution there is just to make sure the pile reaches a high enough temperature to kill those pathogens off. 

Temperature is a super important factor in composting anyhow, one any home composter should be keeping an eye on. But the weirdest reason it's tough to compost meat and dairy is how delicious soil microbes find animal protein. 

And even though composting is all about getting friendly soil organisms to break stuff down for us, we don't want them to get too excited.

Good composting relies on the ratio of two elements: carbon and nitrogen. Carbon makes up the chemical foundation for practically all of life's favorite molecules, including proteins. But proteins also contain a lot of nitrogen, which means that animal products - which are more densely packed with proteins than veggies - contain more nitrogen.

Experts have determined that the best ratio of carbon to nitrogen in compost is somewhere between 20 and 30 to 1. Veggie scraps are generally right in that sweet spot at 25 to 1, but something like a chicken carcass is more like 5 to 1. And when bacteria see all that nutritious nitrogen in a compost pile, they go a little bonkers. They start to grow really fast; that uses up oxygen, and when the bacteria use up all the oxygen in the pile, that favors the growth of other bacteria that don't need oxygen to live.

Basically the pile switches to anaerobic, or oxygen-free, decomposition. And the chemical products of that process are very smelly, like hydrogen sulfide which smells like rotten eggs. So, if you just causally toss your meat and cheese into your compost pile, you'll probably end up with a slimy, putrified mess, instead of lovely fertilizer. And putrified compost can actually contain chemicals that are toxic to plants, though you might be able to salvage it if you dry it out and try again.

To avoid taking those extra steps, expert composters might add extra wood chips or paper products to the pile, since they have a lot of lignin, a tough component of plant cell walls which doesn't contain any nitrogen at all. Bacteria can still eat lignin-packed materials, so they just slow down those overly enthusiastic microbes.

And if you really want to compost meat at home, you could plan ahead. One way is you could rely on a method called Bokashi, which relies on anaerobic methods on purpose. Basically, you add cultures of friendly anaerobic bacteria instead of the bad smelly ones.

Once things like meat scraps have been treated with the Bokashi method, they can be added to a compost pile with less risk of the whole thing going stinky. So just because your municipal compost service won't take meat, it doesn't mean it can't be composted.

You just have to know how to rein in your bacterial buddies. So you can turn basically anything you eat into compost, that's pretty cool. and your table scraps aren't the only household waste you can use to green your garden of course. You make a bunch of fertilizer every year, that you just flush away.

Yes, I'm talking about poop. Because it turns out that human feces can be use as fertilizer. And there's some surprising upsides to this idea.

I'll throw it back to Hank to explain.

To those of you who saw the Martian and walked away wondering if you could actually use astronaut poop to help you grow potatoes on Mars, the answer is yes. You can also use astronaut poop to grow things back on Earth, or just any person.  And while that they might sound a little gross, we humans have been using our own feces for fertilizer for thousands of years. And we are still doing it through what are called Biosolids. Solids from wasted water that have been processed to make then safer.

There are actually a lot of ecological benefit to using biosolid, So some experts argue we should be using more of them. But questions about their safety remains, so researchers are still studying how best to recycle our poop. The danger with feces, be it cow, or chicken, or human.

Is that they can contain some nasty pathogens, that's because many microbes and parasites have evolved to spend their lives in other critters guts, and move between hosts via the fecal-oral route, which... I don't need to explain that, right? If nothing is done to kill those off, then they could end up on any crops that use manure for nourishment.

And that is a real good way to start an e-coli, or salmonella outbreaks. So  if you want to safely use human poop as fertilizer. You first have to make sure that disease-causing bacteria and parasites are dead. The traditional way to do that is composting, which is when you let a massive heap of wet waste from living things: vegetable peels, chicken bones, even poop.

Just sit around until it's broken down by bacteria,worms and fungi. Will not just sit there.

You have to mix it occasionally to aerate it, so our decomposing buddies can get the occasional influx of oxygen needed to continue breaking the stuff down. That process generates a surprising amount of heat.  A compost pile can get up to around 71 degrees Celsius, which is enough to at least kill off most of the pathogens assuming you're doing it right. Which means in theory you could make fertilizer from human poop on Mars or just at home.

And yes, there are people who do this, there are special toilets for it and everything. But most people in the US leave biosolids production to sewage treatments plant. Commercial biosolids produced from wastewater are regulated by EPA.

Anything derived from human waste that's destined to be fertilizer must have a virtual absence of pathogens, according to the agency standards. So these biosolids tend to undergo both biological treatments similar to composting and sterilization procedures. Though there are several different methods used.

The 2017 study estimated that; publicly owned sewage treatment centers produce about 7.2 million tons of biosolids every year, half of which makes its way onto farms.  That is a lot of processed poop, but it's only about half of the total amount of solids that the facilities produce the rest remained as sewage sludge which has to be disposed of through incineration or in landfills. And less than 1% of U. S farms fertilize with them, so we could potentially ramp up the use of biosolids by quite a lot.

The biggest reason to do this would be that biosolids are green.  Instead of sewage ending up in waterways or landfills, it gets repurposed to resupply depleted soil with nutrients. Recycling for the win! And pound-for-poun biosolids are also generally cheaper to make than synthetic fertilizers.

Together that means they could make the biggest difference in countries that struggle with sanitation by composting human waste. Countries could make cheap fertilizer and improve the health of their citizens at the same time, a win-win.

But they'd also be pretty great in the US (or anywhere, really). Becaus their disposal is costly and harms the environment.

So by recycling sewage treatment plants save money and help mother nature but while the upsides are clear, there are scientists and organizations that are weary of the idea. The issue isn't the gross factor, its what else ends up down the drain. Like pharmaceutical compounds, cleaning agents and heavy metals.

While biosolids are considered heavily regulated those regulations don't cover absolutely everything that could potentially hrm us. And studies have shown that such concerns aren't completely without merit.

A 2009 EPA survey found traces of pharmaceuticals, steroids, and flame retardants in various treatment plants' biosolid samples. In a study in a 2012 study found that earthworms and biosolid treated soil, had taken pharmaceuticals and other stuff like disinfectants from antibacterial hand soaps. But it's unknown if this actually harms the worms or could harms us.

Even the lead researcher on the worm study called the risk speculative, while the benefits of using biosolids were clear, there's also the risk that solids could promote superbugs. Microbes that are resistant to multiple or all known antibiotics.

Resistance is a concern whenever are exposed to levels of antibiotics below what kills them outright. And that can happen with biosolids, because many of the antibiotics we take end up in our urine and feces. We know resistant bacteria are found in sewage and sludge, prior to the treatment process to make biosolids and sometimes, after depending on the method used.

So it's possible that these bacteria or their genes could be spread when biosolids are used or produced, but some method that seem to be better at killing these bugs than others. So scientist need more information about what works best and why. That way, they can find ways to recycle our poop without contributing to the crawling problem of antibiotic resistance.

So we just have to collect more data, not poop, we've got plenty of poop. There are also efforts to find other safe uses for biosolids, like a coalition of agencies in the San Francisco bay area looking into using them to generate electricity.

Biosolids could be turned into biofuels cutting down on our need for oil, or even be converted into building materials for some seriously eco-friendly housing. No plans in the works for Martian compost piles yet though, I guess we're just gonna have to wait for Elon Musk on that one.

 Well now I'm weirdly excited about biosolids. Let's say you've got your fertilizer and your garden is starting to grow. You 're all set. Right?
Wrong, if you're not careful your beautiful garden will be overrun with weeds, and in an instant, some hungry slugs or a swarm of aphids can totally undo your hard work.

That's why people use pesticides...but, are they really safe?
Olivia is here with the lowdown.

If you've heard anything about pesticides, it's probably about how toxic they are. Pesticides after all are meant to kill living things, and you're living thing. It seems like it makes sense to avoid them. 

At the same time though, pesticides do a lot of good things for us, like protecting us from diseases like malaria and typhus. And increasing the amount of food we can grow. Most farmers , even organic farmers, use them. 

Naturally there's been a lot of confusing about these chemicals. So let's clear some of that up, here's what science has to say about; what exactly pesticides are? how do they work? and how much you need to worry about the effects on us and our planet?

You might think of pesticides as primarily what's sprayed on your corn or lettuce, but the first thing to realize is that they're actually a really broad category of things. They're basically anything that's used to kill or control pests. Which can be animals, plants, insects, fungi, and bacteria or other microbes.

That means the term pesticide, actually covers a vast array of products. It includes herbicides for destroying weeds. Insecticides for getting rid of insects, fungicides for keeping mold from growing. Rodenticides for poisoning rats and mice, as well as everyday disinfectants. So sure, there may be residues on your apple. But pesticides are also hiding in places you might not think, like your plastic shower curtain to prevent mildew, and in paint to keep bugs in check . We'll be focus on pesticides in agriculture though, because that's one of the largest sources of exposure for most people. Much of the modern concern over pesticides, goes back half a century.

Around then scientist and environmentalist began to notice problems with some of the newer synthetic or man-made pesticides, available after World War two, included one called DDT. DDT acts on sodium channels in insects neurons, forcing them to stay open, and to keep firing. This causes bugs to spasms & twitch, eventually paralyzing and them killing them.

DDT was masterful at eliminating the insects that spread malaria, typhus, and dengue fever, so much so, that the scientist who discovered this property won a Nobel prize in medicine in1948. The chemical worked as insecticide on crops, too.

But it didn't come without cost, although it's moderately safe for humans to handle at low doses. But DDT builds up or bio accumulates in the fat tissues of exposed animals. And because the pesticides degrades so slowly in the environment. It moves up to food chain in a process called biomagnification.

As a result, birds of prey struggled to reproduce because their eggshells thinned and broke more easily. DDt also proved to be highly toxic to fish and other aquatic animals. Basically. it's not good for ecosystems.

In 1962, Rachel Carson famously sounded the alarm in her book: Silent Spring, and a decade later the US government banned DDT for agriculture use. In his own way though, DDT helped to spark the modern environmental movement. People started to cared more about the chemicals used to grow their food and how they affected both our planet and other people.

More care was put into developing and using pesticides, and we have gotten a lot better and more careful with them. But evenly today, it's still not a perfect system. Some of the more modern insecticides, such as the organophosphates, don't stick around as much in the environment as DDT, but they're sometimes more toxic per application. Others, like ones called neonicotinoids, improved on both these fronts.

But they may still be too toxic to certain species, like bees, that we'd want to keep around; scientist are still debating this. Herbicides also have their problems, while insecticides tend to interfere with the nervous system of insects. Herbicides attack weeds by preventing them from growing.

Often they do this by preventing photosynthesis or by inhibiting enzymes that plants use to make new cell walls, amino acids or fatty acids.  Unfortunaley under certain conditions and concentrations some of these are so acutely toxic to humans that people have used them to commit suicide. Others are less dangerous to people and some other animals, but they can still leach into groundwater where they can harm fish. And even though we're making progress, other types of pesticides, have their own struggles too.

Really, none of these are ideal. It'd be great if we didn't have to use them, and there are strategies people can use to reduce use,  but when you run into a big problem. Like a massive cockroach infestation in your kitchen, you'll be glad they exist.

And let's face it, pesticides make throwing food more cost effective. Studies suggest that farmers lose at least 20-40% of their crops to pests, and pesticides allow growers to keep on large scale-production. That means, food is cheaper.

It doesn't just apply to regular produce either, it also applies to the fancy organic stuff. Many people assume organic food, at least as it's legally  defined in the U. S, is grown completely without pesticides, but that's not true.

Organic farmers are supposed to do everything they can to avoid using pesticides in the first place, like rotating which crops they grow, because many pest only attack certain crops. Swapping out different plants in your field, can prevent any one of them from gaining a foothold.

But it those methods fail, and often they do. Organic farmers are allowed to spray pesticides, they just can't be man-made, although there are a few exceptions. Perhaps because of this, and because people generally trust natural things over the ones humans cook up. Many consumers have assumed that synthetic pesticides must be worse than natural ones, but that's only sometimes true.

Some synthetic pesticides are definitely worse. But just because something is natural doesn't mean it's better. Arsenic is completely natural but that doesn't mean you want to use it.

In fact, before DDT came on the scene. Most American farmers used arsenic-based pesticides. Now, no one is using them to grow food. Another example is rotenone, a tropical plant extract that's great for killing bugs, since it gums up their mitochondria. It's also 100% natural, but it wreaks havoc on fish, and has been linked to increased rates of parkinson's disease among farm workers.

Because of other regulations, farmers can't use rotenone anymore. But at least right now, it could still be on some imported organic produce dosage. As toxicologist are constantly reminding us, is also really important. Some scientists have pointed out it's not always clear-cut which might be better: a one-time spray of a synthetic pesticide, or repeated larger doses of a natural one.

The research is still ongoing, but a least one study in soybeans, found that because natural pesticides were less effective, using them ended up actually harming more unintended targets. So the rules then, are really arbitrary when it comes to synthetic versus natural pesticides. 

Mostly don't assume that just because something is organic, and it's been grown with natural pesticides, that you're better of. It's not as clear-cut as you'd hope. Obviously all of this isn't great for consumers, which includes all of us, because we all need to eat, but even though we're still working out the kinks with modern pesticides. You don't need to go and toss out all of your produce or anything.

The U.S government carefully monitors the food supply for excess pesticide residues. So even if some make it into your groceries, you're going to be fine. The Environmental Protection Agency (EPA), sets limits, or tolerance based on the available scientific data for the highest level of residue that's still safe. They also build a margin of error that's at least 10 times, but often a hundred times higher than any study had suggested might be harmful. 

And in the vast majority, 99.5%, of our food supply meets that high standard. So when you hear about  certain foods being full of pesticides, there may be residues there, but they're still well below any known harmful level.

Like for one pesticide, you'd have to eat more than 700 times the typical daily apple consumption to reach the EPA's already cautious tolerance level. Of course, the monitoring program isn't perfect. It doesn't test all food for all pesticides. And it doesn't test for most organic ones. That means that comparing one organic apple to a conventional one, isn't really fair. It's kind of like comparing apples to oranges, so to speak. Ultimately this means you don't actually know the total level of pesticides on each piece of your fruit.

To avoid as many pesticides as yu can, there are a few things you can do, though . You can scrap that outer layer of lettuce or wash your fruits and vegetables, before chowing down. Experts recommend using water, not soap, and rinsing your produce under a faucet. The stream of water removes more pesticides that simply dunking. And rubbing or scrubbing things like potatoes can get you a deeper clean. 

There's no evidence though, that specialty produce washes do anything that water can't do. Washing won't remove every last molecule of pesticide, but does help for most foods. You can also feel  generally better about the pesticide situation these days. Even if things aren't perfect, farmers ans scientist are much more aware of the dangers of them and they've gotten better about use them more carefully. 

So as much as people boom own the good old days of agriculture. Compared with a half century ago, people are ingesting fewer and less dangerous pesticides. Even the most famous ones people love to complain about, aren't that bad. 

One of the most used, and currently hated herbicides us glyphosate, which may be more familiar to you as Roundup. As with any pesticide, it's not perfect but roundup is much less toxic to people and the environment than the vast majority of herbicides. You don't want to sit down to a dinner full of it but all things considered, it's not the worst thing out there.

Of course, that's not to say the situation is ideal either. Farm workers,especially, are still at a much higher risk for a variety of diseases because of their increased pesticide exposure. The long-running health study has been tracking the health of people who apply pesticides for a living for 25 years. It's found that certain pesticides are linked to increased rates 0f rheumatoid arthritis and thyroid problems.

But in general, awareness about the possible dangers of these chemicals to people and the planet. Means we are less likely to indiscriminately use something like DDT before learning more about it. Scientiststoo are working on coming up with new less toxic options for the future. 

One example of these works-in-progress are a chemical called paladins. They're considered fungicides but they don't kill fungus directly. Instead, they help plants fight off the fungus themselves. Many plants, especially those in Brassica family, which includes things like broccoli and brussels sprouts, release antimicrobial compounds to kill their attackers.

The problem is, the fungus have evolved a way to neutralize those defense compounds. It produces an enzyme to detoxify the defense. The idea behind paldoxins is to remove that counter attack and destroy that fungal enzyme to make it easier for the crop to win the battle.

 It's kind of like fixing the match in favor of king broccoli. We don't know for sure how well these would work or how safe they would be. But because it's a very specific way of undermining a certain pest. Biologist think the damage would be pretty much limited to the fungus they want to keep off their plants. And is hard to imagine how this could be harmful to humans.

Other scientists are working on using nanotechnology to do things like control the release of pesticides and stop them  from washing off plants so quickly. That would allow farmers to use less and still get the desired results.

Other teams are looking for different ways to take advantage of the biology of insects, fungi, and other pests to create more targeted treatments.  So hopefully soon thanks to science, we can use fewer chemicals on the pesky organisms out there, and be smarter about it when we do use them. And in the meantime you probably don't need to worry about your salad.  It seems like pesticide technology has been steadily improving over the time, which is great.

Just think about how hard it was to farm ten thousand yeas ago,or when people were just starting to figure all this stuff out. You know what's weird though. We've been doing this agriculture thing for more than ten millennia.

But there are still some things we can't farm, like truffles. Why is that? Hanky poo, help me out.

Food glorious food, we need it to live in stuff but for many people it's more than that, as a hobby, a pastime, a passion. Farms and business work hard to satisfy the commercial and cultural needs of foodies the world over, but not everything can be plunked down in the ground and picked up a few months later. Or grown happily in a tank, some foodstuff just aren't that cooperative. No matter how much we want them, the science of these plants, animals and fungi is at odds with the demand.

Take huckleberries for example, kind of a big deal in the Pacific Northwest of the US, as flocks of people head out into the woods every summer looking to fill their baskets wth the sweet and juicy berries. They're in such demand that huckleberry picking season is now a regulated event in some areas to help make sure there's enough fruit to go around.

You see these berries have a reputation of being difficult to grow in a farm setting. The soil conditions need to be just right. If you're trying to grow them researchers recommend a pH between 4.0 and 5.3 with a mixture of sand, silt and clay to give proper drainage. Additionally in the wild, huckleberry grows at high elevations,this environment provides an insulating cover of snow, to help protect the plant during the sub-zero temperatures of winter. Without this insulation phenomenon at lower elevations, the plants simply freeze, and it's hard to replicate these conditions in other climates. Like imagine like carting a bunch of fake snow and then keeping it frozen, not to mention they just grow painfully slow.

It can take up 15 years after planting seeds or cuttings to yield harvestable fruit. But maybe we're approaching them all wrong, after all indigenous peoples have been cultivating huckleberry crops for centuries, by managing the wild plant.

Say were the ones who taught early European arrivals to North America how to forage for the ripe berries, and over time. This practice of foraging cooking and preserving evolved into the high demand craze that we see every, at least here in Montana.  Researchers have been working on creating a domestic variant of the huckleberry by cross-breeding it with certain strains of blueberries, which are closely related to huckleberries. These cultivars will be able to thrive in a variety of ecological settings making it more likely that the number of crops could rise to meet the demand.

But until that happens, the huckleberry will remain a treat for dedicated berry hunters and only at certain times of the year. And that's not the only luxury food product in high demand. According to sushi lovers, nothing beats the flavour of bluefin tuna.

In 2019,  a single large tuna in Japan sold for over three million dollars. Since fish are only found in the wild, high demand has led to high prices and over-fishing landing the bluefin on the endangered species list. We can't grow these fish in hatcheries yet, because bluefin tuna, have a complex life cycle making them difficult to farm.

They are really big fish. Like over 3 meters long and averaging 250 kilograms They are fast swimming migratory fish, meaning that their natural habitat is much much bigger than any tank. And they need to swim to develop properly.

Plus they are predators at the top of the food chain, so it takes a lot of energy to produce the animals they like to snack on. So mature
adult bluefin tuna are difficult to care for to say the least, but even as tiny free-floating larvae they're difficult to maintain. A study published in 1991, showed when larvae of one species of bluefin tuna are packed in tightly, they grow more slowly, and fewer of them survive. 

That study actually looked at conditions in the wild, but with an eye toward what would happen in a tank though measure could also taken to avoid such issues. Also larvae may be little but their heads take up most of their size. So they're like a little top-heavy, so tank conditions need to be just right to prevent them from literally sinking, and actually getting hurt when they hit the bottom. Because of their size, it can take up to 8 years for them to reach sexual maturity and spawn more fish.

And fish in captivity often experience reproductive issues. Researchers in the EU, and the US. Are trying to overcome these issues by manipulating the fish's own growth hormones to induce reproduction. If we can't establish captive populations to keep up with demand overfishing is likely to continue. Which could be bad news for this fishy favourites.

Other high demands foods are at risk of becoming in danger too-the truffle is the poster child of expensive luxury foods. Some varieties of truffle can sell for hundreds of dollars per ounce. But this fungus could go the way of the dodo. Unless we figure out how to  grow it ourselves. See, truffles aren't like the mushrooms you're probably familiar with. They grow underground, in close proximity to the root systems of trees, usually hardwoods. 

They're mycorrhizal species, which means they have a symbiotic relationship with the trees in which they exchange nutrients and aid each other's growth. but humans haven't been doing a good job of caring for this fungus. Because deforestation and climate change are major threats to the forest across southern Europe, that truffles call home in the wild.

And they're costly and difficult to grow in a farm setting, mostly because it takes time to grow a fungus with such a complex life history. One researcher in the UK harvested his first truffle almost ten years, after planting the Holly oak tree that will develop a relationship with the fungi.

However there might be a small silver lining to the role that climate change has taken. Even though the native habitats of truffle fungi are being destroyed, areas in more northerly forests in Europe may be growing more amenable to these species. Given time, the ecosystem changes from climate change might just provide the opportunity for truffles to move to brand new habitats.

Our demand for these foodstuffs outstrips the supply and it seems unlikely that sushi fans or huckleberry lovers will let them go anytime soon, so we may need to apply some clever science in order to cultivate them. In addition to farming though, this may be the incentive we need to preserve native habitats for the survival of all species, including the delicious ones, because after all, isn't biodiversity the spice of life?

I don't think I've ever thought about tuna as something you can farm. But it totally makes sense, and now that I think about it, I have seen salmon and other fish labeled as farmed. I need to know more, luckily there's an episode for that. Here's Olivia to tell us about aquaculture.

Humans have been eating seafood for thousand of years and in many ways is awesome. Animals like fish don't produce as many greenhouse gases as, say, cattle do. And also they're just plain delicious. Sorry, non-fish-eaters. 

Unfortunately, getting this kind of high quality protein isn't always easy. Some animals don't grow fast enough to be a sustainable food source, and others taste pretty gross for at least part of the year. So to solve these problems, scientists have turned to a maybe unexpected field: genetics.

By carefully breeding or modifying aquatic animals, they found ways to get us more efficient, responsible, and delicious meals. And if you're a seafood fan, the odds are good that you've encountered at least one of these three examples on your plate. Our first example is catfish. Every year, the world consumes hundreds of millions of kilograms of these fish. But the animals only grow so fast, so since the 1960s, the catfish industry has been collaborating with researchers to get those crispy fillets to our plates more sustainably.

One way they've been doing this is by cross-breeding species of catfish, trying to find a hybrid with the most commercially desirable traits. And, they found one. It's a cross between a female channel catfish and a male blue catfish, and appropriately, it's called the channel-blue. This hybrid is bigger, and is better at converting food to body weight than either of its parent species. It also has a higher survival rate and improved disease resistance. The verdict is still out on how and why this happens, but the hypothesis is that the channel-blue just ended up with a really useful combination of genes.

Unfortunately, you can't just throw channel and blue catfish in a pool and wait for them to produce tasty offspring. These species rarely mate with each other in the wild. To get a channel-blue, you have to do things like treat female channel catfish with hormones to induce ovulation, then mix in sperm from male blue catfish.

Don't get me wrong, this method is effective. In 2011, about 20 percent of the catfish harvested were channel-blues. But it's not always successful, so the next step for researchers is to find a way to breed these species more efficiently. Among other things, some scientists are trying to do this by mapping the genes of both parent species. They're hoping to find genetic markers that could someday help channel and blue catfish mate more readily. So maybe we'll be seeing more of these hybrids soon. 

Catfish isn't the only seafood we're interested in improving though. Another example is oysters. Oysters aren't as widely consumed as catfish, but people do love slurping them down and the demand for them is growing. The problem is wild oysters don't always contain a lot of good meat.  During spawning season, they're smaller with mushy, runny flesh and their gonads take up around 40% of their body mass.  For real.  Some could call them the ballsiest creatures on Earth.  That just doesn't sound appetizing.

So scientists found a workaround.  They made commercial oysters sterile.  They did it by engineering triploid oysters.  These are oysters with three sets of chromosomes, one more than normal.  This odd number messes with their ability to produce sperm and egg cells, which means the animals have more energy to devote to growing fatter and tastier.  

Scientists started experimenting with triploid oysters in the 1970s and 80s, but while they did achieve some victories, their methods weren't good enough to go widely commercial.  They were creating triploids by applying chemicals to recently fertilized eggs, and that wasn't always successful and didn't go over well with the public, so in 1993, scientists tried a modified approach.  

First, they combed through the triploid oysters from previous experiments and found the rare exceptions that were somehow still fertile. Then, they took the oysters' eggs and injected them with sperm cells containing one more set of chromosomes.  Ultimately, this led to the creation of a tetraploid oyster, one that had four sets of chromosome, and when that animal mated with a normal oyster with two sets of chromosomes, it produced sterile triploid offspring.  Today, this idea is what leads to those fat, juicy oysters you order at restaurants.  So not only is the food fancy, but the science is, too.

Now, as weird as they might be, neither hybrid catfish nor triploid oysters are considered genetically modified, because they weren't engineered by directly transferring specific, deliberately chosen genes.  This last example, though, is a proper GMO.  In fact, it's the first truly GMO animal to hit the market for human consumption. It's called the AquAdvantage Salmon.  

Unlike wild oysters and catfish, wild Atlantic salmon are already pretty good at converting food into body mass, but scientists wanted to create an even more efficient version, because like, have you tasted salmon?  Don't you want more of that?  To modify this animal, researchers took fertilized eggs from wild Atlantic salmon and inserted two new components: the growth hormone gene from a Chinook salmon and a short bit of DNA called a promoter from a fish called an ocean pout.  

The Chinook gene was chosen because compared to Atlantic salmon, these salmon tend to grow more from the same amounts of food, and the ocean pout promoter was chosen because it allows the pout to grow year-round, as opposed to the Atlantic salmon, which only grows during certain times.  These researchers essentially took two beneficial traits and threw them into one organism.  

They also made the salmon triploid and sterile, to make sure they could never mate with wild salmon, even if they somehow escaped captivity.  The AquAdvantage fish was tested for safety and approved for sales in early 2019, and compared to its wild counterparts, it grows faster and reaches the same size with 25% less food, so more salmon for us.  Projects like these are major ways we can continue eating seafood without taking as much of a toll on wild populations and habitats.  They won't solve all of our problems, but these clever, creative ideas do have the potential to really improve sustainability.  

Michael: Scientists sure are working on some cool stuff with farmed seafood. And that's just a drop in the bucket when it comes to agriculture tech. It's funny, because while we have made some pretty impressive innovations over the past 12,000 years, our farms don't look that different from the farms of our ancestors. But agricultural technology is advancing rapidly, and in the near future, food production could look very different. Here's Stefan and Olivia to give us a glimpse of what's on the horizon.

Olivia: Many people around the world already have a hard time getting access to food, and as the population grows, the demand for it is only going to increase. Eventually, a day might come where we don't have enough space, energy, or water to make enough food for everyone.

Stefan: The good news is, scientists are already preparing for that day. Here are three innovative technologies already in the works that could transform the future of food.

Olivia: First, as popular as meat is, it also takes a lot of land and energy to raise animals. And in the future, we might not have enough resources to get everyone that particular type of protein. Back in the 1960's, one company developed a meat substitute with this concern in mind. It's called mycoprotein, and instead of being made from jackfruit or beans you might find in a typical veggie burger, it's made from fungus. Specifically, the most common one is made from a strain of Fusarium venenatum.

To make it, the fungus is fermented in a reactor with carefully controlled acidity, temperature, and amounts of nutrients. Then, it's combined with a binding agent and mixed up until it's roughly the texture of meat. According to people who've tried it, it apparently tastes pretty good. Making mycoprotein takes significantly less land and energy than it takes to produce meat. And the process generates up to 90% less carbon dioxide. It also has more protein than tofu. Unfortunately, it's also caused some people to have severe allergic reactions. And one survey of a thousand people suggested mycoprotein sensitivity could be more common than shellfish or peanut allergies.

So, if this is going to be a long solution, we'll either need to find some way to test for those allergies or find a different strain of fungi to use. And, since researchers have already tried thousands of them, that could be tricky.

Stefan: Thankfully, growing fungi doesn't take up much space, but if we want to eat something besides Mycoprotein in the future, we'll likely need more land. Right now, more than 40% of Earth's land is used for agriculture, and there's only so much fertile ground left. That's where another idea, called aquaponics comes in. It's a form of hydroponics, which is growing plants in a water and mineral solution, not in soil. But instead of getting those nutrients from a commercial fertilizer, aquaponics uses the waste from fish farms. To do it, you raise a bunch of fish in a relatively small area, but keep filtering the water to remove any toxins. As the fish go about their lives, breathing and pooping, the water becomes full of helpful minerals and nutrients like nitrogen. Then, those pass into a separate chamber and are filtered out by plants. In some models, the plants are just sort of held over the water so that their roots dangle into it. At the end of the process, you have a bunch of happily fed crops and clean water that can go back into the fish tank. The main benefit here is that you can set up an aquaponics farm anywhere, since they work indoors. But, there are some kinks we'll need to work out first.

For example, fish can provide almost all the nutrients a plant needs, but getting the right balance of them can be difficult. Pest control is also much harder since adding pesticides to the water could kill the fish. You also need a bunch of fish, which could get kind of pricey, especially if you're trying to do this in a desert. Still, some farmers have already had success with this method on a small scale, so if we keep working on it, maybe we'll all be eating fish fed plants someday.

Olivia: Besides aquaponics, there's another way we could get around a future farmland shortage. We could build up instead of out. This idea is called vertical farming, and it involves growing plants in stacked containers, like on shelves or different floors. So you could basically turn a skyscraper into a farm. This concept was first proposed around 2009, and it's already been successful in tests. Plus, it can also be combined with other technologies like hydroponics.

The biggest benefit to this method is that it uses way less land. If you built a 30-story farm on one city block, you could grow almost 100 times as much food as on a traditional farm of the same size. Since these farms are indoors, you also wouldn't have to worry about the weather or most pests. And if you used filtered wastewater to irrigate your crops, you'd basically have the perfect city farm.

Then again, you would also need to construct a giant, custom made building to make this work, and that wouldn't be cheap. And you would need a way to get your plants enough sunlight, too. One option would be to use artificial lighting, which has worked relatively well on current hydroponic farms. You could also rotate plants throughout the day to get them equal time near windows or skylights. Possibly the biggest challenge, though, is that vertical farming isn't very eco-friendly. At least not yet. One 2015 analysis of a small farm calculated that vertically growing lettuce produces 2-5 times more carbon dioxide than lettuce grown in open fields. Most of that probably came from powering the building, since running artificial lights and irrigating crops uses a lot of electricity. We could make this technology greener by using cleaner sources of energy, but since that's not the only hurdle, it'll probably be a while before cities are the new farmlands.

Michael: What's cool about these new technologies is that they're not just for large farms. You can employ them at home to take your gardening to the next level. Like, you can build your own hydroponic setup in your backyard, or start a vertical farm in your apartment. And, we could all eat less meat, and more mushrooms. Thanks for watching this episode of Scishow and thanks to our patrons who made it possible for us to create all these videos. It takes a lot of different people to make a Scishow episode, and we couldn't keep making them without your support. If you like what we do here, and would like to learn more about how to support us, head over to patreon.com/scishow

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