Steady States: From a Party to Earth’s Surface Heat

Imagine a social get-together in a reception hall. For about an hour after the start of the alcohol-free cocktails, new guests keep arriving. Feeling a little crowded inside, some guests decide to leave the hall to step outside for a stroll through the property. At a certain point it works out, as a result of their reflexes, that the number of people walking into the hall is the same as those walking out. Since the number of guests inside the hall is constant, we have what’s called a steady state. As long as the input of new guests equals the output of existing guests, steady state is maintained. A more sombre but far more important steady state involving humans would be achieved if we could stabilize world population by lowering birth rates to match declining death rates. (Long extraterrestrial journeys won’t be economically or technologically feasible in the foreseeable future and won’t serve as output rates.)

Many essential and approximate steady states occur at the molecular level. They involve  compounds and elements that are part of natural cycles. For instance, the amount of phosphorus in both land and sea would approximately be at steady state if humans recycled it. Phosphorus is an essential element and is found in nucleic acids such as DNA and RNA but also in molecules involved in cellular energetics such as ADP and ATP. The key is the polyatomic ion phosphate (PO43-). In the soil, microorganisms break down plant debris and animal waste to release the ion. Some phosphate from rocks is also added to soil. But the soil’s input rate is balanced by the output rate when plants uptake the essential ion and runoff removes some phosphate before plants can absorb them. When phosphate is added to land on an industrial scale without  corresponding recycling practices, then the output rate into rivers and oceans is accentuated. Snce the 1950s, the environmental flow of phosphorus has quadrupled; steady state has been thrown off, impairing marine freshwater and marine ecosystems.

Schematic-view-of-the-coupled-biogeochemical-cycles-of-carbon-nitrogen-and-phosphorusAlthough natural cycles are often introduced as separate phenomena in textbooks, in reality they are integrated. For example the phosphorus and carbon cycles are tightly coupled. There is evidence that between 23 and 150 million years ago, spanning the late Jurassic , Cretaceous, and Paleogene periods, the phosphorus cycle has not always been at steady state. It seems to have been affected by episodes of global warming.

steadyState
If the outflow rate around the loose plug equals the rate of water pouring out of the faucet, the amount of water in the sink is in steady state.

On that note, can there be a steady state involving heat? Although heat and temperature are not the same concept, since the number of air molecules in the atmosphere is approximately constant, when one is fairly steady, so is the other. Imagine the amount of heat at the earth’s surface represented as the amount of water in a sink. Above the sink we have a faucet gently turned on, but we also have a loose plug over the drain. If the inflow rate from the faucet is equal to the the amount of water that seeps around the loose plug and goes down the drain, the amount of water in the sink will be constant.

Now imagine tightening the plug ever so slightly.  The water in the sink starts to rise, but eventually the extra pressure from the extra water’s weight above the drain helps establish a new steady state. The difference between the current and prior  states is that we now a higher, albeit constant, level of water in the sink.

Getting back to the analogy we started: if water represents heat, then the plug is represented by water vapour and carbon dioxide in the atmosphere. Since the concentration of water vapour is far less affected by human activity than CO2, it’s the addition of the latter to the atmosphere that tightens the plug. If we can stabilize carbon emissions, then although we will have a higher average global temperature than pre-industrial levels, we won’t be entrapping more heat.

Can there be a natural corrective action like the effect of gravity in our analogy? After all, the geologic record reveals that the earth has repeatedly experienced changes  in CO2 concentrations. Before answering the question, we have to be careful and point out an important characteristic of real-world steady states. Natural systems involve many factors and create complex, cyclical steady states, not flat lines. The graph below reveals that for over half a million years, the CO2 concentration has oscillated from about 180 ppm to under 300 ppm. (Even if we had never burnt fossil fuels, in merely one year, due to seasonal variations, carbon dioxide peaks and ebbs—with a much lower amplitude of course.) But the current, human induced 410+ ppm-spike in CO2 has been unprecedented in over half a million years. Given that it has taken an average of 100 000 years to get a drop of only 120 ppm,

waiting for a natural correction would bring about too many negative consequences for too many species, including our own.

Achieving approximate steady states involving ions, gases and heat is what our living earth does in the long stages between catastrophes.  It’s time for our politics, technology and lifestyles to be in tune with the time-tested cycles of geology, biology and climate.

Sources:

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Marcel Laurin Woodland Park

p1130047The Marcel Laurin Woodland Park is all too easy to under-appreciate. Drive or cycle by it too quickly, and it could easily go unnoticed because of its size–it’s not one of Montreal’s largest regional wooded areas. But once inside the woods, one realises that it is a special part of Montreal’s parks and protected woodlands, which combine to hold 75% of the city’s approximately 1.2 million trees. It gives citizens easy access to wildlife, which is key since not all can afford to travel far to experience it. Still a long way to becoming a mature forest, the woodland  is in part a wetland . Especially in the springtime,  the water that it collects allows dead leaves and other lingering organic material to decompose, increasing the availability of nutrients. These lead to a diversity of fauna and flora.

Some of its Fauna

mating_ball_of_garter_snakes
Source Wikipedia

The common garter snake (Thamnophis sirtalis), like all reptiles in Quebec, is not poisonous to humans. It’s a good thing because after ignoring my advice, a student of mine once picked up a baby garter and was lightly bitten on the thumb. When defiant students are not around 🙂 ,  the snakes feed off the woodland’s slugs and toad-eggs. The adults form a mating ball consisting of several males competing for a single female, which eventually gives birth to live offspring. They were considerably widespread on the island as far back as the 1960s when I remember seeing garter snakes on a weekly basis during my childhood in St. Leonard. But that suburb of Montreal, like the rest of the city, has lost most of its wetlands. A stream that once ran through the former St-Leonard site has totally disappeared and though memories of some citizens have not yet faded, the biological diversity in many areas is long gone.

c095e
This 1832 map shows two areas of Montreal including (1) the current site of Marcel Laurin Woodland and (2) St-Leonard described in the text. Large sections of the island had already been deforested for the sake of agriculture. But we can see persistent streams(highlighted) and associated wetlands that no longer exist but which influenced the type of vegetation and animal life on our island. Source: James Wyld (1812-1887), David Rumsey collection

The availability of nutrients in the wetland makes the area rich in insect life which attract a variety of birds. In the Marcel Laurin Woodland, I’ve seen cardinals throughout the year along with wood peckers, birds that are rarely seen by citizens in the more densely urbanised sections of the island. Thanks to the efforts of amateur ornithologists who reported their sightings to Regroupement Québec Oiseaux, the organisation was able to include them in the ÉPOQ database.  Here are some of the ones people and I have spotted in the woodland. From left to right are the the black-capped chickadee (Poecile atricapillus); the eastern kingbird (Tyran tritri); magnolia warbler(Setophaga magnolia); hairy woodpecker (Picoides villosus); and the least flycatcher (Empidonax minimus). (The first pic is mine and was taken in Marcel Laurin; the rest are from Wiki)

The city’s website reports that

the woodland holds a certificate from the University of Kansas’ Monarch Waystation Program, and in 2009 it received significant support numerous partners for the planting of native grasses and milkweed necessary for the Monarch butterfly’s feeding and reproductive needs.

I have yet to see monarchs in the park, which does not necessarily mean they don’t come by, but I also noticed some replanting of milkweed late in the summer of 2016.  Thus the project described above is still a work in progress.

Some of its Flora and an Unwelcome Guest

Drawn to the borders of the Marcel Laurin’s stream are two dominant species, the silver maple and the red ash. One of the drier areas also has a small strand of at least 20 scattered beeches. A few years ago, invasive species such as the European and adler buckthorn were removed to help indigenous species such as the ash and maple, when suddenly the former was invaded by the Emerald Ash Borer (EAB), an insect whose larvae can girdle and kill trees. The threat is serious because 1 in every 6 trees in Montreal (and the majority of trees in Marcel Laurin Woodland) is an ash. In the past two years the city of Montreal has been forced to cut almost 8000 thousand severely infected ashes on the island. In that same time period, 37,000 infected trees have been treated with TreeAzin

ash-borer-lifecycle
(A) egg (B) larva (C) the EAB adult. Source: Phil Geib, Chicago Tribune

The insecticide consists of a 5% solution of azadirachtin, a compound found in neem seeds.

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azadirachtin from chemSpider

It is biodegradable and shows very low toxicity to mammals. It actually doesn’t kill the insects; it prevents the destructive larvae from developing. The reason that the larvae are so destructive is that until the late 1990s EAB was only found in eastern Russia and China, where the insect and ashes coevolved. Continuous election created a balance where EAB could complete its life cycle without killing trees. But in North America, in only about a decade, EAB has spread like wildfire from Michigan to Quebec and all the way to Texas. Out continent’s ash trees lack defensive mechanisms and compounds that are used by trees in Area where the insect is indigenous. In addition, our ash trees on this continent release compounds like hexanal, linalool and 13 other volatiles whose signals are picked up by the antennae of adult EAB , facilitating insect-movement from one host to another. This happens when they are chewing on the leaves. As the larvae develop they  feed off the phloem, tissues that transport sugars from the leaves to the roots. The bark of the ash tree releases sequiterpene-compounds like α-cubebene, which also helps EAB adults locate a tree. And with more guests invited, enough tissue can be damaged to kill the tree.

What has not helped Montreal ash trees in the face of this EAB epidemic is climate change. Drought weakens trees, making them more vulnerable to insects. Winter temperatures below -33 º C are needed to kill dormant eggs. Montreal’s winters have been milder in recent decades. Environment Canada records indicate that we have not seen -33 º C in February since 1994; December  temperatures have been above -33 º C since 1980, and in the last four years, the coldest January temperature was only -24.6 º C.

Other Sources:

Review of the emerald ash borer (Coleoptera: Buprestidae), life history, mating behaviours, host plant selection, and host resistance
Therese M. Poland, Yigen Chen, Jennifer Koch, Deepa Pureswaran.  The Canadian Entomologist. 147(03): 252-262.

https://www.nrs.fs.fed.us/disturbance/invasive_species/eab/biology_ecology/host_preference/

Life is hazardous and short for Montreal's downtown trees

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