Is global warming good for plants?

Some people deny that global warming is happening. Others agree that it is happening, but claim it isn’t a bad thing. People in this second group often say that global warming isn’t bad because all that extra carbon in the air will promote plant growth, which will benefit agriculture and the environment. Is this true?

Not really.

As described in the last post, plants do need carbon to grow, and they like having more of it around. But, they like extra carbon a little too much.

Let’s explore why by looking at humans and sugar.

Humans like sugar. We generally think of sugar as a bad and unnecessary thing that makes us fat. But, in fact, humans need sugar. In the past, sugar was rare and hard to find. Because sugar was important for human nutrition but difficult to get, evolution fitted us with a sugar craving that drives us to search energetically for this nutrient, and consume it whenever possible. This worked great until the modern age, when sugar became abundant and readily available in our dietary environment. Our biology hasn’t yet learned that it should tell us to eat a certain amount of sugar and then stop. And so, unless we manage to exert a lot of willpower, we end up eating too much sugar, and we get sick from it.

A similar mechanism is at work in plants. A plant’s biology tells the plant to absorb as much carbon as possible. This is very good for the plant as long as the amount of carbon the plant can realistically absorb is not greater than the amount of carbon the plant really needs. However, if a plant was able to absorb more carbon than it needed – for example, due to rising carbon levels in the atmosphere related to global warming – then the plant would happily gorge itself on the extra carbon. In a classic case of too much of a good thing, the plant would then become sick.

This is not just theoretical. Studies have found that plants that binge on carbon really do become unhealthy. Just like humans who eat too much sugar produce body fat that isn’t good for them, plants that absorb too much carbon produce abnormally high levels of starch. And while these plants are getting vegetatively flabby, they store less protein in their pollen.

This means that the plants are not healthy, their pollen does not contain the nutrients that pollen-eating animals need to be healthy, and the parts of the plants that humans eat are similarly lacking in nutrients that humans need to be healthy. Far from being a boon to agriculture, global warming puts plants on a junk food diet that is bad for everyone.

And that part isn’t theoretical either. Studies on how plants react to excess carbon haven’t just been done in the lab. In the US, plants living in the wild have shown a marked decrease in the protein content of their pollen since America began industrializing in the 1840s. That decline has been most severe over the past six decades, when America’s carbon emissions were increasing dramatically.

Global warming is a serious problem that we are running out of time to solve. At this point, we cannot decrease our emissions steeply enough to avoid disastrous warming on our planet. To prevent the worst impacts of climate change, we need to not only reduce our emissions, but also actively work to take carbon out of the atmosphere.

Humans have not yet invented technology that can take carbon out of the atmosphere. Fortunately, nature has. We call that technology plants.

Global warming will not benefit either humans or plants. But if humans and plants work together, we still may be able to solve this urgent problem.

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Is global warming good for plants?

How can we help plants?

In conventional gardening, plants are treated like yard furniture: inanimate objects that we can arrange and modify to suit our own preferences, and which will quickly fall into a degenerate state if we don’t constantly maintain them. This is, of course, biologically inaccurate. With a few exceptions, even highly cultivated plants are essentially wild creatures that, given appropriate growing conditions, can take care of all their own needs. Plants don’t require our help.

How do we know that this is so? Quite simply, because plants thrived on Earth for million of years before humans appeared on the scene. In contrast, humans literally would not survive for one day without plants.

Some people, in recognition of this fact, truly want to repay plants by helping them out. This is wonderful. However, many of the things that people do – with the best of intentions – to help plants are in fact harmful to plants. Pruning plants robs them of their food-producing ability and leaves them vulnerable to disease. Situating plants in a sea of mulch deprives them of the companions they need to be healthy. And spraying them with pesticides kills the insects the plants rely on for their reproductive processes.

There are some things we can do to help plants, though. Here are three simple actions with real benefits for plants.

Breathe on them. We know that animals take in oxygen and breathe out carbon, while plants absorb carbon and give off oxygen. We usually describe this harmonious dynamic by saying that plants clean the air for us. It is fascinating to realize that from a plant’s perspective, we clean the air for them! By breathing on plants, we can provide them with a little boost of the carbon they need to build their bodies. (It is thought that this is why some people swear plants grow better if you talk to them. It’s not the words we’re saying that benefit the plants; it’s the air we’re blowing on them.)

Relieve yourself on them. As described in a recent post, human bodily waste is full of nitrogen, a nutrient plants need. When we excrete on plants, we deposit nitrogen in a form plants can use. In contrast, when we excrete in modern toilets, we deposit nitrogen into the water supply, where it contributes to harmful effects. (Unless you are way out in the woods, though, don’t literally excrete on plants. Find a happy medium in the humanure process.)

Don’t walk near them. Some plants like to be walked near: for example, those that stick their seeds to our pants and let us disperse their offspring. For the most part, though, walking near plants only contributes to soil compaction and damages the plants’ roots. Resist the urge to hug trees. Instead, tell them loudly, from a respectful distance, how much you appreciate their service. They’ll enjoy the extra carbon more than they would the warm embrace.

How can we help plants?

Why is That Blog necessary?

That Blog has now been active for three years, and currently has nearly 200 posts. Those posts document numerous benefits of natural yards, and also report on clear signals that the era of the lawn is rapidly coming to a close.

During that same three-year period, however, the acreage of lawn in the United States has continued to increase, alongside ongoing suburban sprawl, as lawn remains a default landscaping choice in many parts of the country. And, studies still find that many people do not understand or value the many crucial services that urban nature provides for us.

A fascinating report from 2015 – just after That Blog was launched – investigates why experts on the importance of urban nature struggle to communicate what they know to laypeople. The fundamental finding of this report is that while experts recognize that nearby nature is absolutely critical to human health and wellbeing, the average person views nature as a sort of bonus amenity that is nice to have around if there is any space left after inserting houses, schools, workplaces, roads, parking lots, and all the other manmade infrastructure a community needs.

The report finds that many people also struggle with the basic idea of nature in cities. Urban dwellers often don’t view their local parks as nature, despite the presence of trees and other plants. To many Americans, “nature” means someplace vast and far away, the kind of place we visit occasionally on vacation.

In other words, the average person thinks that nature only counts if it’s big, and that we can “stock up” nature to sustain our wellbeing throughout the year. In contrast, experts understand that people benefit from nature as small as a pocket park or a residential yard, and that we need daily exposure to nature to really be at our best.

After comparing the views of laypeople to the knowledge of experts, and examining the communications gap between the two groups, the report concludes that people would value and support urban nature more if they understood that:

  • nature benefits us even when it is small.
  • we benefit from experiencing nature, rather than simply using it as a place to take a walk and get exercise.
  • nature benefits us in specific ways, via mechanisms science can explain.
  • nature is an essential component of urban design; we cannot live without it.
  • we can choose to have more nature in our cities!

For three years, That Blog has examined how even a small planting provides a wide variety of benefits, explored how we feel when we look at naturally-growing plants, explained how plants support our physical and mental health, expressed that natural yards are a great choice for our neighborhoods, and encouraged everyone to garden sustainably with nature!

Until public understanding and acceptance of urban nature is in line with what experts have long known, That Blog is still necessary. In the coming months, That Blog will cover the impacts of global warming, how to be a good neighbor to plants, and what happens to people’s wellbeing when nearby nature is destroyed. But first, That Blog will tackle head-on the key question: How can one yard make a difference?

Why is That Blog necessary?

What is an invasive species?

In the last post, That Blog asked what a native plant is. Asking what an invasive plant is might seem redundant – if it’s not native, it must be invasive, right?

Actually, no. If it’s not native, it must be non-native. But not all non-native plants are invasive. An invasive plant is one that meets a special definition:

An invasive plant is one which tends to spread, and which causes harm to the local ecosystem.

A non-native plant that stays put in a garden, or that escapes into the wild but causes no discernible disruption to the existing plant community, is not considered to be invasive.

Where do invasive species come from? Some – like Kentucky bluegrass – arrive by accident, as stowaways in other shipments. But half or more of the invasive species spreading across the United States today were deliberately introduced by the nursery trade. People planted these ornamental exotics in their yards, and the plants then cheerfully multiplied beyond the property lines.

In recent years, some states have tried to deal with this problem by banning the sale of invasive species. Some of these measures have passed; others have not. Even when they do pass, though, they tend to ban plants which have already been sold in abundance, and which have already spread into natural areas. Once a species has invaded an area, it is usually very difficult to eradicate. Banning the continued sale of such species is unlikely to make a dent in the problem.

An approach that might be more effective is to make every property owner responsible for eliminating invasives from their own land: if we each take care of our own piece of the Earth, together we might be able to accomplish something. Municipalities have used this approach for a long time, in the form of banning so-called “noxious weeds”. But these weed bans are often not enforced, and, more importantly, they tend to take aim at plants that are unpopular, rather than focusing on plants that are truly harmful. As just one example, these rules often forbid milkweed, the family of native flowers that are crucial to the survival of the monarch butterfly.

Before we pause to reflect on That Blog’s third anniversary, let’s take a look at one more definition worth knowing: a naturalized plant is not one that has settled harmoniously into its new home. Rather, it is a non-native species that is capable of surviving and reproducing without human help; in other words, a species poised to become invasive.

What is an invasive species?

How do I know what plants are native?

So you’ve decided to garden with native plants. Great! But… which plants, exactly, should you put in your yard? What is native?

The concept of nativeness encompasses two aspects: space, and time. First, where was the plant in question found before humans started moving it to new places? Many resources will answer this question by noting whether a certain plant species was historically found in a particular state. But this is a somewhat arbitrary criteria. Plants don’t know or care about the political constructs we call states. And large states may contain many diverse ecosystems. A species might naturally occur in the forests of northern California, but that doesn’t make it a suitable choice for a yard in the arid southern part of the state.

This is why some resources list native plants by county. But even this doesn’t really have anything to do with the way plants naturally distribute themselves. A plant that has historically lived just over the county line might be a better fit for a site than a plant found in a distant corner of the same county.

For this reason, some native gardeners skip native-by-county and native-by-state lists entirely, and instead look at distance. Any reputable dealer of native plants will be able to tell you where they got the original seed from. (And it should be seed. Reputable dealers do not sell plants taken from the wild; they propagate seeds in their nurseries and sell those plants.) If that naturally-occurring source of seed is within, say, 50 miles of the intended planting site, then the species is native. If the seed is being collected from further away, it is not native, and won’t be considered for that particular garden.

The other aspect of nativeness is time. When we say that a species was found somewhere historically, what do we mean? Kentucky bluegrass, which originally evolved in Europe, could be found across the eastern United States 100 years ago. Does that make it native? What about plants that lived in the northern states prior to the last ice age, got wiped out by the glaciers, and haven’t come back on their own yet? Are they native?

Most people say that if a species was found in a place just before the time that Europeans got there, then it is historically native. But as climate change continues to alter ecosystems, we may want to update our definition of historically native to mean “species that were found in that place when the local climate was similar to what it will be again in the near future”.

Many native gardeners are not purists – that is, they will plant a non-native species in their yards because the species has especially beautiful flowers, or produces delicious fruit, or simply is a personal favorite of the gardener. There is nothing wrong with this. But if we are serious about native gardening, we should at least be aware when a species we are planting is one of these special exceptions. To do so, we first must decide how we are defining what is or is not native in our own yards.

How do I know what plants are native?

How can you establish a natural yard faster?

As explained in the last two posts, natural yards take a long time to establish, and attempts to speed up the process often backfire. There are, however, a few ways to help nature happen a little more quickly.

Inexperienced gardeners – natural and otherwise – often think that the short route to a well-established yard is to bring home the biggest plants they can fit in their cars, and put those plants in the ground.

In a sense, this works. By following this strategy, the homeowner may be able to enjoy trees as tall as a person, fully leafed-out shrubs, and blooming flowers on day one of their gardening efforts. But what happens after that?

It comes as no surprise that plants don’t like to be moved. Plants have spent millions of years evolving to make the best of whatever spot they germinate in. They have no evolutionary experience of moving to a new spot and getting resettled. Plus, transplants typically have spent the first part of their lives being coddled in a greenhouse, and don’t appreciate being relocated to an outdoor spot, where they suddenly have to put up with wind, irregular watering, less-than-perfect soil, and all the other challenges associated with life as a plant.

The older and bigger a plant is when it gets relocated, the more trouble it has dealing with the unexpected event and all its related challenges.

Experienced gardeners have noticed that if they plant two trees – one older and larger, one younger and smaller – at the same time, by a few years later, the tree that was initially smaller will have grown bigger than its partner. This is because the originally-larger tree struggles more to re-establish itself, and so takes longer to resume investing its energy in growth. The smaller transplant, in contrast, will settle into its new home more easily, and will soon return to vigorously putting on height, width, and foliage.

It’s also worth noting that smaller plants are generally cheaper. Given a limited budget, there is a certain satisfaction in bringing home one sizable tree and planting it in the yard. But buying three smaller trees – or several dozen flower seedlings – will result in a complete, healthy planting, as opposed to the gardener being left with one lonely tree surrounded by lawn.

For those gardeners equipped with patience and foresight, seeds may be an even better choice than small plants. Given that seeds can be installed in the yard by the simple expedient of throwing them on the ground, and given that seeds will turn themselves into plants that provide a host of benefits and then go on to create more of themselves, it is astonishing how inexpensive seeds are. Reputable dealers will sell their product in terms of pure live seed – that is, if you want one ounce of seed, and the dealer knows that this species has a germination rate of 50%, they will sell you two ounces for the price of one. This way, you know you are always getting your money’s worth.

By taking our time, we can establish our yards more easily, more cheaply, and more quickly. Gardening is an endeavor in which slow and steady does, indeed, win the race.

How can you establish a natural yard faster?

How long does it take to establish a natural yard?

Many of us today want things as fast as possible. We like high-speed travel, instant coffee, and websites that load in a millisecond. Maybe this is part of why natural yards have been slow to catch on in America.

Unlike lawns, which can go from bare soil to goal state in a few weeks, or annual flowers, which come home from the garden store already blooming, natural yards take a long time to look like we envision. Experienced natural gardeners say that it takes about three years for a natural yard to “come together” and begin resembling what the gardener had in mind.

Why so long? First, because in a natural yard, the gardener is strongly encouraged to wait a year before even beginning to do anything. And second, because natural yards tend to focus on plants that expect to stick around for the long term – and long-lived plants take the slow and steady route, rather than rushing to flower in their first summer.

The native prairie plants of the American Midwest, for example, spend their first few years investing all their energy into the root systems that will sustain them over the coming decades. They grow just enough leaves to photosynthesize a little, and often don’t attempt to bloom until about their third year. People who aren’t familiar with prairie plants and their life cycles think that these baby perennials look like weeds. Well-intentioned gardeners who don’t adequately prepare themselves for the establishment phase think that their plants are failing, tear out the seedlings, and start over. The wise gardener waits patiently, and is ultimately rewarded with beautiful, thriving plants that are ready to take care of all their own needs.

How long does it take to establish a real prairie – a prairie that is indistinguishable from the few undisturbed remnants that remain in the Midwest? Scientists estimate that the answer is somewhere between 100 years and never.

The oldest prairie restoration in the world is located at Madison’s Arboretum. The planting was established about 80 years ago by the best experts available at the time (with hundreds of people helping to do the physical labor), and to a trained eye, it is still not the same as a remnant prairie. If a small army of the most dedicated, most knowledgeable people cannot truly restore a prairie in eight decades, it is unsurprising that the efforts of a home gardener take at least a few years to even begin looking like a prairie.

It’s similar with other types of ecosystems. A forest is not really restored until at least the second generation of trees has reached maturity, a process that can take decades to over a century. The Holy Wisdom Monastery (located in Middleton, a suburb of Madison) has started to restore 30 acres of its property to oak savanna – a type of ecosystem found across southern Wisconsin before European settlement – but will not even begin to plant understory species until the trees have matured, 20 years from now.

Even a desert takes a long time to restore. You can plant a Saguaro cactus, but it will take fifty years or more to grow its distinctive arms.

Natural yards teach us patience. There is not much a gardener can do to hurry up the process. In the next two posts, That Blog will look at some strategies that don’t work, and then some that do.

How long does it take to establish a natural yard?