Why do we need nature in every neighborhood?

People often toss around the words “appropriate” and “suitable” to describe where they think nature belongs. Nature is “appropriate” in city parks. Nature is “appropriate” in faraway wildlife refuges. Nature is “inappropriate” in people’s yards.

We should be asking these people why they think it’s “appropriate” to deprive others of a healthy living environment.

It’s a fact that some neighborhoods have more nature than others. In particular, affluent neighborhoods tend to have more street trees and more green space than poorer areas of the same town. Now, of course, there are lots of reasons why rich people are doing better, in all sorts of ways, than those who are less financially advantaged. There are also reasons why wealthy neighborhoods are greener: for example, those with money and status are more likely to demand that these kinds of amenities are created and preserved.

Presumably, the well-off would not be demanding more trees and parks if they thought these things were bad for them. But the more important point is that there are direct links between more greenery and being better off. Experts say that access to nature tends to move people towards healthier patterns in their exercise routines, transportation choices, and diets. Nature also reduces stress, moderates temperature, and combats air pollution. When people don’t have access to nature, they don’t have access to these important benefits either.

It’s fairly obvious that people who have nature right outside their front doors have more access to nature than people who have to travel some distance to experience healthy plants and plant communities. People who have more access to nature and all its benefits are more likely to actually receive those benefits.

The city of Madison recognized this when it said that destroying trees in some neighborhoods and not destroying trees in other neighborhoods would be unfair to the residents of the de-greened areas. It was exactly because of this unfairness that the city decided to work harder to protect trees.

In saying that it’s not fair for some people to have more trees and some people to have fewer trees, the city of Madison was expressing that trees have value. Nature has value. And so, to return to the original point – why would it be “inappropriate” to have valuable things on our property?

Nature belongs in every neighborhood – in the form of pocket parks, street trees, and natural yards – for the same reason that every neighborhood should have fire hydrants and nearby places of employment and access to public transportation. These things make our lives better. Anyone who says otherwise is not acting in your best interest.

Advertisements
Why do we need nature in every neighborhood?

Where is deforestation happening?

When we think about deforestation, we think about the Amazon rainforest: iconic images of towering jungle trees being cleared to make room for ranching operations, and statistics about how many football fields per minute are being lost.

We may also think about the Canadian boreal forests, huge swathes of which are being leveled so that fossil fuel companies can extract the tar sands oil that lies buried beneath them.

And we may think of America’s Pacific Northwest, where it seems that environmentalists and loggers are constantly at odds over whether old-growth trees should be harvested for commercial use or preserved to provide wildlife habitat and inspire awe in each new generation of humans.

What most of us don’t think about is urban areas. But American cities are losing trees at an alarming rate. One study found that between 1975 and 2006, Minnesota’s Twin Cities region lost 14% of its forest cover. Percentage-wise, that’s actually more tree loss than the Amazon rainforest experienced over an equivalent period.

And a study published this past spring estimated that urban areas of the United States, taken as a whole, are losing 36 million trees a year. That’s net loss – the total decrease in the number of trees after adding back newly-planted trees. Dividing up the data by state, the researchers found that in recent years, only three states have seen a net increase of urban trees, and then only by tiny increments.

As explained in an earlier post, that’s a problem because trees in cities aren’t optional. When there aren’t enough trees around to absorb stormwater, clean air, moderate extreme temperatures, and give people a little relief from the stresses of modern life, providing all of those services through other methods ranges from expensive to impossible. The end result is that we pay more in taxes and get back a lower quality of life.

We can reverse this trend. First, we can demand that our local officials respect and protect our urban trees, instead of damaging or destroying trees that pose minor inconveniences. Second, we can actively work to plant a healthy next generation of trees. No matter how well we care for mature trees, they will eventually die. When that happens, it is too late to plant a replacement tree – it could be decades before the new, young tree is able to provide benefits equivalent to what its adult predecessor was doing. Instead, we need to nurture an urban forest in which every canopy tree has a younger companion nearby, ready to quickly take over the older tree’s duties when its life inevitably comes to an end.

Where is deforestation happening?

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?

What is soil compaction?

In previous posts, That Blog has covered properties of soil, such as soil types and soil pH. One property not yet written about is soil looseness.

Good soil, gardeners say, should resemble chocolate cake – in both its color and its crumbliness. Good soil has lots of air in it. Why?

First, because these channels and pockets of air also serve as pathways and holding places for water. As discussed in the previous post, we want water to move down into soil. Loose soil structure helps that to happen. Soil that is dense and hard will resist water, leaving it pooled on the surface, where it will either cause flooding, or run off to cause flooding somewhere else.

Second, because the air spaces in soil provide room for roots. Plant roots grow easily through loose soil. Under these conditions, plants are able to find nutrients, absorb water, and anchor themselves securely. In contrast, roots struggle to penetrate soil without air, leaving the plants sickly and weak.

Soil without air is compacted soilSoil compaction is events and processes that lead to compacted soil.

What kinds of things cause soil compaction? One major perpetrator is development: covering soil with pavement is, of course, not good for the soil. Another cause is heavy vehicles. A bulldozer or brush hog may be the fastest way to clear a site of unwanted vegetation and prepare it for new plantings, but these huge machines also cause serious damage to the soil on the site, making it more difficult for the new plantings to get a start in life.

Even lighter vehicles are tough on soil. ATVs can cause compaction and damage, which is one reason some people oppose the use of ATVs in natural areas. And finally, a person on foot is heavy enough to squash down soil and destroy those crucial air pockets.

For this reason, treehuggers may want to curb their desire to hug trees. When we walk up to a tree’s trunk, we are stepping on its critical root zone – the area directly under the tree’s canopy, where its roots are most actively performing their vital functions. Compacting the soil in this area can be very detrimental to a tree’s health. While some tree species – such as those that have evolved to live in perennially soggy areas – are adapted to compacted soil and able to withstand those conditions, many other species suffer from the suffocation of their roots.

Humans like hugs. Trees are indifferent to them. In a few weeks, That Blog will look at simple things tree lovers can do that trees will really appreciate.

What is soil compaction?

What’s new in natural yards? May 2018

A recently-published study (authored in part by That Blogger’s former thesis advisor) examines how Wisconsinites think about their urban trees.

A 16-page survey sent to homeowners in and around Milwaukee, Madison, Green Bay, and Wausau asked people a variety of questions about trees. One set of questions regarded benefits and problems related to trees. Under the header of benefits, survey respondents most strongly valued trees for their ability to make a place look nice, provide shade and cooling, improve air quality, and generally enhance the livability of a neighborhood.

But about half of the homeowners said they were “strongly concerned” about the risk of trees or branches falling and damaging things. People within city limits (as opposed to those living in the suburbs) and people with smaller lots tended to be more worried about this risk, possibly because a falling tree or branch on their property was more likely to hit something. People who saw trees as dangerous, the study found, valued trees less overall.

The survey also asked who homeowners trusted for help and advice related to trees. The results showed that respondents trusted tree professionals more than any other source of information. Averaged across the four cities, 62% of people said they would trust a landscaping company or tree service, while only 14% said they would trust the staff of a non-profit organization. This is surprising and worrying, as such professionals have a financial incentive to suggest whatever service is most profitable for them, rather than the service that is best for the tree and its neighbors (human and otherwise).

The survey’s demographic questions turned up some interesting findings. Women rated trees more highly than men did, and millennials valued trees more than baby boomers, though these younger folks tended to have fewer trees on their own properties, likely because their lots were smaller than those of their more senior neighbors. Older homeowners, in contrast, expressed more concern about trees “growing too big, making a mess, or blocking scenic views”.

Finally, most people who answered the survey thought that their neighbors valued trees and took good care of trees. But, as with many domains of life, people rated themselves even more highly on questions about recognizing the importance of trees and properly caring for trees.

The relatively-brief, highly-readable report can be found here.

What’s new in natural yards? May 2018

Why do some trees keep their leaves later into the fall?

The intuitive answer is that a healthy, vigorous tree will keep on photosynthesizing late into the fall, while a weak, sick tree will give up and go dormant earlier in the season. In fact, it’s exactly the opposite.

When it comes to the problem of how long leaves should be held onto, a tree faces a dilemma. On the one hand, a tree can only produce food and store energy while it still has its leaves. But on the other hand, as winter creeps closer, having lots of green leaves is a big risk – the leaves could be killed suddenly by a frost, or they could catch flakes in an early snowfall, causing weight to pile up on the tree and increasing the likelihood that branches will break.

In the normal course of things, a tree wants to store all the energy that its leaves have produced, reabsorb the chlorophyll and other useful chemicals from its leaves so they can be used again the following year, and then jettison the leaves and ride out the winter in a dormant state. Ideally, all of this will happen just before frost arrives, thus maximizing photosynthesis and minimizing the risk of frost damage.

Of course, the tree doesn’t know exactly when the first frost will arrive, and so it has to take a bit of a gamble with its timing.

A healthy tree that has stored up plenty of energy for the winter will play it safe, losing its leaves well before cold weather sets in, and relying on its reserves to last until spring. Conversely, a tree that is struggling will run the risk of being injured by a night of freezing temperatures in order to squeeze in a few more days of photosynthesis, in the hopes of storing enough food to make it through to the next growing season.

Thus, trees that settle in for winter early are doing well, and trees that cling to their leaves are desperately trying to survive.

Why do some trees keep their leaves later into the fall?

Why do trees lose their leaves and branches?

The common understanding is that a tree’s leaves die at the end of the summer, and then fall off. This isn’t quite accurate. It’s more correct to say that the tree kills its leaves.

What’s really happening is that the tree builds a layer of cells inside the leaf’s stem to create a seal that blocks the flow of nutrients to the leaf. Imagine putting a tourniquet around your arm and leaving it there: eventually your arm would die and fall off, and that’s exactly what happens to the leaf.

A similar thing happens with branches. Humans, like most other animals, start their lives with a fixed number of limbs, and don’t get any more. For this reason, we’re very interested in keeping our arms and legs intact. But a tree can grow a new limb pretty much whenever and wherever it wants. When a branch isn’t pulling its weight, the tree will kill it – by creating an internal seal and starving it to death – and then grow a new branch that contributes more to the tree as a whole.

When a leaf or branch that has been killed in this way falls off, it doesn’t do the tree any harm. The tree wasn’t using that body part anymore, and the internal seal prevents any infection from entering the living parts of the tree. In contrast, when a leaf or branch is broken off suddenly – perhaps due to a hungry herbivore, pruning, or a powerful windstorm – the tree loses a healthy, productive body part, and acquires a wound through which insects or fungal infections can easily enter. Because trees don’t do anything very quickly, it can take them years to seal even a relatively small wound – more than enough time for a serious infection to set in.

It’s therefore inaccurate to say that cutting off a tree’s limb doesn’t hurt the tree. Of course, it doesn’t hurt the tree the same way that it would hurt a human, because the tree can regenerate. But the loss of a productively photosynthesizing branch, coupled with the energy demands of sealing a wound and growing a replacement branch, can put serious stress on a tree. While pruning may be desired for other reasons, the idea that pruning is good for a tree’s health just doesn’t cut the mustard.

Why do trees lose their leaves and branches?