I’ll let you in on a secret: Plants have besties  and frenemies.

They form exclusive cliques — no,  you can’t sit with them. And don’t even get me  started on their love lives.

Love triangles? No,  please, try love octagons. While it’s easy to think of plants   as existing in individual bubbles, nothing  could be further from the truth.

In reality,   they’re constantly interacting with other  organisms in their environment. Plants’ social lives are as dynamic as those in  a supernatural/horror/crime high school drama.   And dishing about plant interactions isn’t just  the tea; it’s essential to their conservation. In  order to respond effectively to threats  like climate change and habitat loss,  we need to know how plants fit into the  social fabric of their environment.

Hi, I’m Alexis! And this is Crash  Course Botany. [THEME MUSIC] How we relate to one another is a big part  of our everyday lives — for better or worse.   In the school cafeteria, you might see a  math wiz and a history buff helping each other   with homework, but you also could  catch a confrontation between the drum major and the star of the spring musical. This sort of thing happens all the time in nature, too — close interactions between two different  species are known as symbiosis.

And plant ecology,   or the study of relationships among  plants, organisms, and their environments,   is a huge field. So, let’s start zoomed  in, with one-on-one interactions. Like, plants and fungi are often best buds,  swapping beneficial nutrients underground   through the plants’ roots.

The fungi’s  filaments, or thread-like structures,   are the perfect conduit for trading food  with plants— and hot goss, probably. This type of mutually beneficial relationship  is called, appropriately, mutualism. Another classic example of mutualism  is between plants and pollinators,  like butterflies, birds, and bats.

They get tasty food in exchange for  helping plants reproduce. And there are some  lesser-known pollinator pals, too— even gerbils.   In South Africa, they pollinate the  Massonia flower by carrying pollen from   plant to plant on their furry snoots. Plants can also participate in commensalism,   where one species benefits and the other is just…  meh, neutral.

Take ferns and bromeliads—the family   that includes Spanish moss and pineapple  plants. Many live on the branches of trees,   and while they don’t actively harm the trees,  they don’t do them any favors, either. But not all social arrangements are good for,  or neutral to, the plant.

Many interactions   are considered parasitism because the benefit  to one species comes at a cost to the other.   Mistletoe, for example, is a parasite that grows  high up on a tree’s branches. But unlike those   bromeliads and ferns, which just kinda hang  out on their trees, mistletoe sucks water   and nutrients from its tree, which can stunt its  growth. Not exactly a Hallmark movie moment.

Even those plant-pollinator interactions can  sometimes head into parasitic territory. There’s an orchid that mimics the shape and scent of  female wasps, so male wasps waste valuable   energy and sperm trying to mate with it, while  the plant reaps the benefits of pollination.   And, there are insects that rob nectar from  flowers without transferring any pollen at all. Talk about some toxic friendships.

Understanding all of these different interactions   isn’t just useful for a plant teenager trying  to survive Botany High. It’s also crucial to conservation, or the protection of species diversity from threats like climate change and habitat destruction. After all, we can’t restore wildflower meadows  without their pollinators, and saving rare bromeliads can’t happen if there are no trees for them to grow on.

In other words, all plants are connected   to other organisms, so conservation has to  consider those networks of relationships. Anyway, now that we’ve covered the scale of  one-on-one interactions, let’s zoom out a level   to look at groups of the same species living in  the same place. In other words: populations.

Populations change over time — they grow or  shrink. They rearrange themselves into different   patterns, or distributions. And often, these  changes are influenced by environmental factors.   These shifts and the forces that trigger them  make up the field of population ecology.

And by studying these types of population  changes, population ecologists can learn   things that go beyond a single species. Take Mimosa scabrella, a species in the pea family that’s native to Brazil. It tends to be one  of the first species to regrow in areas that have   been disturbed by harmful human activity.

That’s because the tree is super adaptable   to different soil conditions, even those that  have been depleted by things like mining. And as it begins to regrow, the  plant makes the area more hospitable   for other species to do the same. So, the distribution and abundance of this   population in a damaged area is a good indicator  of how well the area is recovering overall.

But while Mimosa scabrella is a conservation  hero on one hand, it presents  conservation challenges on the other. It only grows natively in one place—   making it an endemic species. And  endemic species are particularly vulnerable   to environmental changes or events.

Think about it: for widespread species, a forest fire might wipe out a local population. But  for an endemic species, that wiped-out population   might be the entirety of the species. So, population ecologists monitor,   and sometimes alter, populations for  conservation purposes.

Like, the Holy Ghost Ipomopsis is a particularly extreme example. This homebody is endemic to only a two-mile stretch of a canyon in New Mexico. And ecologists are using two strategies to conserve it.  One is in-situ conservation, which  takes place in the plant’s native habitat, and   involves clearing debris that could fuel forest  fires, and trimming back other plants that are encroaching on the Ipomopsis’s territory. The other is ex-situ conservation, where new populations are started outside the species’ natural habitat.

Botanists are growing lots of Ipomopsis in  botanical gardens so the species won’t be   lost to a disaster. And once the plants  grow strong, the ecologists reintroduce   some of them back to their native habitat  in an effort to expand the population. So, we can study individual species through  population ecology.

But we can also zoom out   one step further to consider how groups of  different species interact in a shared space.   This is the focus of community ecology.  To witness community ecology in action,   let’s head to the Thought Bubble… Welcome to Florida’s Everglades, one of the world’s largest wetlands. Its combination of salt and freshwater, varied soil types, and subtropical  climate has led to a diverse community of plants  and animals. Ooo!

Look there’s lots of saw-grass over here which can thrive even in low-nutrient soils,  and provides shelter for nesting alligators. I respect you from a distance, large lizards! Then there are the spatterdock plants,   which provide cover for frogs and fish and  whose seeds are eaten by ducks—yum.

Underwater, manatees feed on seagrasses. And on land, mahogany and oak trees provide a habitat for other plants to grow, like bromeliads and ferns. On top of that, the Everglades are home to the   largest mangrove tree population in the western  hemisphere, which not only form habitats locally,   but also help shield those inland plants,  animals, and people from storms.

But in the early 1900s, nobody really  knew about this complex community.  Most Floridians thought that the area was a useless  swamp, and developers started to drain it so they could build on the land. Enter the journalist and activist  Marjory Stoneman Douglas. In her later years, Douglas was determined to save the Everglades.    She wrote articles and published  a book that was kind of a love letter to   the swaying saw-grass we saw before.

Her writing made a huge impact on public opinion— and Floridians began to recognize the  value of this ecological community. And in 1947,   the Everglades National Park opened,  which formally protected it. Thanks, Thought Bubble!

So, plants live their  lives in the larger context of communities,   and they can play huge roles in  shaping their environments. Like,   one plant species might help others grow more  by making the environment less harsh.  Community ecologists call this dynamic facilitation. And  the Big Sagebrush plant is a pro at it.

In North America’s deserts, water is pretty  scarce, which is a challenge for plants with   shallow roots. But when Big sagebrush sends  its super-deep roots far into the soil to   search for water, it brings that water up  to the shallow-rooted plants as well. On the more dramatic side of things,  plants also engage in competition,   where they make the environment more  difficult for other species to survive.

Most plants compete with each other for light  and nutrients — a little healthy competition   isn't so bad. But some plants secrete  chemicals from their roots into the soil   to prevent other species from sprouting nearby  — and that is a little more cutthroat. And competition can get really out of  hand when invasive species — or species   from another area — come onto the scene and  totally disrupt ecological communities.

For example, a major invader in the western  U. S. is cheatgrass. It was introduced to the   region accidentally in the 1800s, likely  because its seeds got mixed in with other   agricultural products.

Now you see, the problem  is, it grows back after the winter thaw earlier   than native species do, so it sucks up the  water supply first. Those meanies. It also produces a lot of plant material  that can become fodder for fires, and it   can re-sprout super fast even after a fire  rolls through.

So, it quickly dominates the   habitat and pushes out native species. This has huge effects on the ecological community — delicate relationships are disturbed,  soil is degraded, and essential nutrients are intercepted. This all makes it harder to restore  the area after it’s been disrupted.

The good news is there are many conservation  efforts happening worldwide to protect plant   communities from threats like habitat loss  and the effects of climate change. And, at the local level, your country’s  forest service likely provides resources   on how you can reduce harm from invasive  species in your own community. This might involve things like removing  contaminated soil, or even digging up   the plants themselves.

Because, yeah, you  exist in community with your local plants.   Whether you realize it or not, you went to  the same high school. Well, sort of. Whether they’re interacting one-on-one,  as a population, or in a community,   studying the ecological dynamics of plants  at all these different scales gives us the   knowledge necessary to conserve them.

Because a community isn’t the same without each   plant that exists within it, just like a high  school isn’t the same without every athlete,   mathlete, rebel, and artist  that grace its hallways.   Next time, we’ll be checking out the role  of plants in different ecosystems—  spoiler alert: they’re at the bottom of the  cheer pyramid—er, food chain. Hey, before we go, let’s branch out! What  is a characteristic feature of flowers   pollinated by geckos?

The answer  can be read in the comments! Thanks for watching this episode of Crash  Course Botany which was filmed at the   Damir Ferizović Studio and made in partnership with  PBS Digital Studios and Nature. If you want  to help keep Crash Course free for everyone,  forever, you can join our community on Patreon.