Urban Nature

diversity in the garden

Why should you cultivate dandelions in sidewalk cracks, spiders in the attic and mushrooms in lawns...

Now that spring has fully arrived, I’m spending time weeding my garden. Volunteer plants have sprung up everywhere, like, well, weeds. I’m not pulling everything out - much to the annoyance of my neighbor who claims my few dandelions are an eyesore even though millions are in the park across the street.

Even in an urban environment (like where I live), we’re still part of nature. Urban living doesn't have to mean surrounding ourselves with a concrete jungle; we can still make room for diversity in nature. Even the dandelion that takes root in a tiny crack in the pavement and the moss that grows on your roof counts as diversity.

Diversity is important because it adds a complexity that makes an ecosystem stable. A single change that destroys one species is not a big deal if many species fill that niche, but a very big deal if it was the only species. For this reason, any ecosystem with only a few species is vulnerable. Consider a lawn containing a single species of grass - soon weeds will move in or nutrients will be used up, forcing the owner to take drastic action like applying herbicides or fancy synthetic fertilizers. Or, consider diversity in relation to our food crops: using a single variety can result in crop failures and no back-up to turn to. A sad example is the potato famine that occurred in Ireland between 1845-1852 (from wikipedia article here). Even though there are many varieties of potatoes on this planet, the Irish only planted a select few species and blight wiped them out - bad, bad news.

A diverse ecosystem, in contrast, acts to buffer the effects of change. No one goes out into an old growth forest and sprays the dandelions (although, exotic plants can still invade). My garden, which I pack full off as many different crops into my tiny yard as I can, will always produce me something.

Taken as a whole, the Earth is an example of a diverse ecosystem and can be considered a biosphere. People have dabbled in creating artificial biospheres since at least Victorian times. On a small scale, you can go out and buy an 'ecosphere' which is a sealed glass ball filled with water. Inside the sphere is a little ecosystem consisting of shrimp, algae and bacteria, which isn’t very diverse. In 1986, Carl Sagan wrote a glowing article about these ecospheres called, 'The world that came in the mail'. Their makers say these glass worlds can last up to 10 years, but critics say the shrimp are slowly being poisoned by their own waste while starving. Perhaps a bigger biosphere is needed.

Biosphere 2 (earth is Biosphere 1) is a 3.14 acre sealed greenhouse in Arizona that is broken up into several different types of ecosystems. Each ecosystem included several species that filled the same ecological niche, and soils were seeded with micro-organisms in an effort to enhance diversity. In the early 90's, an experiment was conducted by sealing in eight volunteers to simulate using a biosphere for space colonization. I remember seeing the ad for volunteers and being fascinated with the idea; however I had other commitments at the time and couldn't apply - which is perhaps for the better.

These eight people to be were sealed into Biosphere 2 for two years where they grew their own food. Their atmosphere was also enclosed, so the only oxygen available came from the plants within the biosphere. It turns out the biosphere wasn't a stable system: carbon dioxide levels fluctuated widely and oxygen levels couldn't be maintained. All the pollinating insects died, while cockroach and ant populations overran the place. The people sealed inside couldn't grow enough produce, forcing them onto calorie restricted diets.

One result of this experiment was to demonstrate that creating a stable biosphere is currently outside our capabilities. Since we haven’t successfully made a new biosphere, Biosphere I is all we have. So don't get rid of all the diversity that pops up or moves in. Keep a little diversity at home.

Upside down grazers

possible alien world?

Imagine a world where animals graze on a surface of green extending above our heads. To me this sounds like a scene from a science fiction movie set on an alien world that requires ‘unabtainium’ or a ‘flux-vortex’ to exist. Yet, habitats like this exist on earth. The underside of sea ice is one (caves are probably another).

In the Arctic, the sun returns long before the ice melts. Since first year ice is relatively clear, sunlight can pass through. Algae takes advantage of this light and sets up shop on the bottom surface of the ice. A two-dimensional world is created in the normally three-dimensional euphotic zone.

Ice algae plays an important role at the base of the ecosystem. These algae blooms represent the beginning of the Arctic grazing season as no photosynthesis can occur during the long winter polar night. Since other phytoplankton are scarce this time of year, creatures flock to the icy roof for a meal. Diners include diatoms, protozoa, nematodes, copepods and others. Copepods in particular are a food source for bigger creatures and fish such Arctic cod. These fish are eaten by bigger fish, birds and marine mammals.

Light is critical for ice algae to thrive, so any snow covering the ice can have a negative impact. Too much snow and there won’t be enough light for the algae to grow. Additionally, particulates in the ice can block sunlight. A large mining or smelting operation could coat the ice in particles, blocking the algae’s light.

This ecosystem, like all others on our planet, will be impacted by climate change - and we don’t know exactly what the end result will be. Ice algae need the clearer first-year ice to grow. If warmer conditions made this ice melt sooner, the algae would sink and die. The grazers that depend on the algae would starve. On the sea floor, algae would decompose potentially creating anoxic conditions, a potentially fatal environment for bottom dwellers such as turbot, Greenland sharks and Arctic skate. Or, if warmer conditions result in less multiyear ice, potentially more first year ice could form. Ice algae would have more space to grow and more food could be available for all (assuming there was enough nutrients). 

Image is from here

How to be an algivore

powdered chlorella on a spoon

To start my investigation of algae, I cracked open an old textbook of my husband’s titled: ‘Introduction to Phycology'. According to the textbook, “algae is ubiquitous, occurring in practically every habitable environment on earth.” I agree as I don't have to look far to find algae. My aquarium hosts all sorts of algae types resulting in periodic algal blooms, some less desirable than others. Walking into my bathroom, I can often find a pink alga growing on my shower curtain which would take over my shower if I didn’t regularly beat it back with bleach. Further afield, algae can be found thriving under Arctic ice and in deserts. I doubt there’s a more a resilient plant out there.

Plenty of critters thrive on an algae diet. Back to my aquarium, a farlowella (a stick-like fish with a suction-cup-like mouth) thrives on the green alga growing on the glass. My ever-expanding population of snails also dine on this alga. Out in the wild, frog and toad tadpoles live on algae. In fact, algivores reside all over this planet. Plenty of humans include algae in their diets - and have been doing so for eons. Apparently, ancient Aztecs considered spirilina (a freshwater microalga) a staple. Many coastal communities harvest seaweeds (a type of algae) all over the world and have done so for centuries.

In the alga eating spirit, I've decided to try eating (drinking actually) Chlorella vulgaris daily. Chlorella is a microscopic freshwater green algae. I bought a small tub of it in powdered form. Before I opened the tub, I expected chlorella to smell like pond scum, instead I got a pleasant surprise when the smell reminded me of a hayloft on a sunny day (still not a food smell). The powder is a dark forest green, so dark it's almost black, with the texture of a ground up pigment.

my farlowella kindly cleaning the glass for me

It is easy to find glowing reports about chlorella (which I keep wanting to pronounce as cholera) as a superfood. I'm sceptical whenever the declaration of a 'superfood' is made, especially if the superfood was considered a 'staple' of an ancient remote civilization – everyday food never seems to be declared a superfood. Instead of eating a blackberry from my backyard, am I supposed to rush out and buy acacia berries from South American jungles?

There are documented benefits to eating microalgae. First of all, they contain all sorts of nutrients and complete proteins. Additionally, chlorella can reproduce itself four times every twenty-four hours, making it the fastest growing plant on the planet. This productivity is an important factor in considering food sources for our seven billion plus population. As for the health claims, I just don't know. According to the internet, chlorella is apparently a cure-all, especially useful for 'people with poor vitality' (whatever that means). On the flip side, I've found web sites documenting digestive distress caused by consuming chlorella. I take the hype with a grain of salt.

Another well documented benefit to chlorella is how it improves air. Experiments have shown chlorella absorbs carbon dioxide and replenishes oxygen (important for long space voyages). If cultivated in tanks, eight metres squared of exposed surface is needed to keep one person breathing – which isn't much considering the cultivation tanks could be shallow and stacked. These experiments were conducted in soviet-era Russia (1970s) where they made no effort to eat the stuff. NASA took the next step and looked at chlorella as the sole food source for astronauts on long space voyages – apparently they would survive, but I bet they would be grumpy.

As a food, chlorella poses a bit of a problem. It's a single celled spherical alga with tough cell walls. These cell walls make it impossible to digest in its natural state. Processing of some form is required. Chlorella has a second problem – flavour. I've tried algae (in this case seaweeds) that have tasted fantastic, chlorella doesn't. It isn't that it tastes bad exactly, just unfamiliar. So far, I haven't found any reference on how to make it taste good – just advice on masking its flavour in smoothies, or taking it in pill form. I tried it in a chocolate-banana smoothie, the smoothie was fine but there was no hiding the fact that chlorella was in there.

Ageing maple leaves

a maple leaf in the sun

Yesterday, in the parking lot at work, a maple leaf rested on the pavement. The golden-hued morning light caught the leaf highlighting the red-tending-to-maroon tones. The leaf sharply contrasted the cold grey of the pavement, its vividness catching my eye. What if I picked up the leaf and saved it? Could archeologists in the far future figure out when the leaf fell from the tree?

Currently, we can estimate how old plant-based objects are using radiocarbon dating - often just called carbon dating. In 1949, Willard Libby and his team accurately estimated the age of the wood in an ancient Egyptian barge – a barge with a recorded age. This process works through knowing the ratio of carbon-12 (the ordinary stuff) to carbon-14 (a radioactive isotope) in the atmosphere.

Carbon-14 isn't particularly stable and decays quickly. It has a half-life of about 5,730 years - only a moment of time compared to the approximately 4.5 billion year half-life of uranium-238 (which is roughly the age of Earth). Continuously formed in the atmosphere by cosmic rays, carbon-14 reacts with oxygen becoming carbon dioxide. Plants take up some of this carbon dioxide along with carbon dioxide formed from the more abundant carbon-12. When the plant dies, no more carbon dioxide is taken in and the existing carbon-14 begins to decay.

If we assume the carbon-12 to carbon-14 ratio was the same when the plant died to now, using the decay rate of carbon-14 will give us the item's age (back to about 60,000 years). But, we know this ratio has fluctuated over time. To compensate, the age results are calibrated to something known like written records or tree rings. The biggest change to the carbon-12 to carbon-14 ratio has occurred in modern times through nuclear testing. Carbon-14 levels in the atmosphere were boosted around 1950 and peaked in the 1960's (at which time, testing bans were agreed to).

So, could a future archeologist figure out the are of my leaf using carbon dating? Probably not accurately because we've messed with the carbon-12 to carbon-14 ratio in our atmosphere. It would be more accurate for that archeologist to look at the date of this article.

As a tangent: At the end of the day when I returned to my car, the leaf was still there. Without the sunlight shining on it, the leaf looked brown and uninteresting.

Spider plants

A spider plant inhabits a corner of my home office, in fact I can't remember a time when I didn't have a spider plant somewhere in my home. I poached this particular plant from an off-shoot of a friend's plant and it now has an off-shoot of its own. Based on my reading about spider plants, I think I'll pot up the new off-shoot and create another plant.

Spider plants, or Chlorophytum comosum, originally came from South Africa to become a very common house plant. Their tolerance to some neglect makes spider plants a great plant for busy folks. I don't know what spider plants look like in the wild, but mine is the typical domestic variety with long, spikey green leaves with a white stripe up the middle. I've also seen spider plants with solid green leaves. It isn't my prettiest plant - the tips of the leaves tend to go brown (I hear regular fertilizing can help prevent this) - but what the spider plant does for my indoor air keeps me growing them.

Nicely insulated houses, like mine, can have significantly more polluted air than the outside. In the winter, when windows and doors are kept closed, these air pollutants can build up. Fortunately, cleaning up indoor air has been extensively studied by NASA because an extended space mission can't possibly bring enough air for the whole trip – so the air needs to be cleaned and re-used (the same hold true for water in space).

In a house or office building the most common pollutants include carbon monoxide, formaldehyde and benzene – each comes with its own negative effects. Plants provide an easy, low energy way to remove air pollutants. Since this is not a new idea, a technical term exists – phytoremediation, which is defined as the use of plants to remove environmental pollutants or render them harmless. The most effective plants for dealing with air pollution include: philodendrons, golden pothos, spider plants and chinese evergreens. My spider plant can effectively remove lots of carbon monoxide. Some say a spider plant removes about 560 micrograms per hour of formaldehyde (ref). They go on to say that a spider plant can remove all the formaldehyde in a room in under 4 hours, but, it didn't provide any back up data so I'm suspicious.

More than just the plant does this good work, microbes found in the soil also aid in removing pollutants. To create an optimized plant filter combine the plant and its associated soil microbes with activated carbon* - a combination that is already available commercially.

There is another side though – some argue that plants as air filterers are not that effective in real world rooms (as opposed to controlled conditions in a lab). Plants also increase humidity in a room, which can lead to mold issues if you aren't diligent. I tend to have lots of plants – I enjoy seeing them and believe they improve air quality, although perhaps not as much as some say they do. I think a reasonable additional step is to also avoid adding chemicals to your indoor environment (like cleaning chemicals or particle board furniture) and to air out rooms whenever the weather permits.

*As a tangent – what is activated carbon? It's a small carbon chunk with an extremely rough and porous surface. This creates a huge surface area for the size of the chunk, according to wikipedia: just one gram of activated carbon has a surface area in excess of 500 square meters. This huge surface area is available to bind to pollutants (and other stuff).

Bamboo – the grass that can be almost anything.

So what can I toss into a stir-fry, play a tune on, build scaffolding out of or put on a shirt made from? The answer is bamboo – the fastest growing member of the grass family. Right now I have several hand towels made of bamboo and a bag of bamboo shoots in the freezer. I'm debating planting some in my front yard (although it never looks healthy in neighboring yards so I might not) and flooring my house in it. Bamboo sounds like a miracle plant, but like everything it has a downside.

Wikipedia tells me that grasses can be considered the most important plant group. This group includes the grain and cereal crops people cultivate for food, wild grasses eaten by livestock or other animals, as well as bamboo, from which almost anything can be made. Bamboo shoots can be eaten, they are very tasty in a stir fry and they can be fermented into a sweet wine. Like other grasses, when bamboo is harvested it is cut, not dug up, so growing bamboo can add stability to soils and prevent erosion while producing a viable harvest.

Pesticides are not commonly used when cultivating bamboo. There are a few pests out there that like to munch on bamboo (I suppose pandas would be one), but they can be dealt with manually by cutting out the infested stems. Once the bamboo is harvested, pests become more of an issue. To prevent this, some large-scale operations treat the bamboo with a mixture that can include DDT. Dark flecks in the bamboo is often a hint that that bamboo has been treated this way. Once harvested, bamboo needs to cure. There are many ways this is done from soaking in water for months to burning techniques – it can even stored vertically and allowed to dry naturally. So, now the bamboo is ready to go.

Paper could be made through techniques mastered by the Chinese eons ago. Flutes could be made; I love the haunting sound that a bamboo flute can emit – it seems unearthly. Since I have no musical ability, I won't be making my own flute even though many websites exist to tell me how.

Bamboo fiber is becoming more and more available and is often touted as an eco-friendly option. Is it better than other fibers available? The answer is maybe; it depends how it was made. Bamboo can be made into fiber by two methods. The first, eco-friendly option is similar to how flax and hemp fiber is extracted. Stalks are crushed. Then natural enzymes take over breaking the fibers down more. Finally, the fibers can be combed out and used. The second method is essentially the same as how rayon is made from cotton. Harsh and toxic chemicals are used to break down the stalks and mechanical spinners extract the fibers. The label on my hand towels only say they are made from bamboo, not which method was used in the making of them.

If the first method is used, bamboo has a lot going for it. Like other natural fibers it is biodegradable. From the same sized space, bamboo produces ten times more fiber than cotton while requiring significantly less water. A website selling bamboo clothing says that bamboo fabric is soft (which is true of my towels), anti-fungal, anti-static and even cuts out most harmful UV rays. So, if you need a new shirt bamboo produced the right way is a great option. However, I don't recommend you throw out all your cotton shirts and replace them with bamboo - sometimes the most environmentally sensible option is to get the most wear and use out of the things you already have. But when your cotton shirts wear out, go shopping for a naturally prepared, bamboo shirt.