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I read somewhere that 1,000 square metres of grass absorbs the same amount of carbon dioxide that one person produces. I then think about my small 10ha property. Does that mean that I am covering 100 peoples’ CO₂ emissions every day? What about those large 1,000ha properties then? Do they absorb thousands of tonnes of carbon every year?
In New Zealand, your average carbon footprint will be around four tonnes of carbon, emitted per year (based on the carbon contained in 16.9 tonnes of carbon dioxide equivalent annual per-capita emissions). A 1,000-square-metre area of grass will take up around one tonne of carbon per year. So if you didn’t fly much, lived in a well insulated home, cycled to work etc, you might bring your overall footprint down to around one tonne of carbon per year, the equivalent of what a backyard lawn may take up per year. So far so good.
The big problem (causing tremendous confusion even among scientists) begins right here. In the above, we talk about fluxes, not pools. Using your bank account as an analogy, fluxes are transfers, pools are balances.
With your own carbon emissions, regardless whether they are one or four tonnes per year, you pay into the atmosphere’s account every year. This means that there is more and more carbon in the atmosphere.
That carbon comes from fossil fuels – an entirely different “account”. Regardless of whether you have 1,000 or 100,000 square metres, this is what grass is doing in this analogy: it takes carbon from the atmosphere every year, but that carbon is going straight back to where it was taken from when you mow the lawn and the biomass is broken down and returned to the atmosphere. In other words, your carbon footprint is a flux that leads to a permanent change in a pool (the atmosphere). This is a bit like a weekly salary. You don’t have to pay it back. What your lawn is doing however, is making payments that are returned a few weeks or months later (when you mow the lawn, a cow eats the grass, or when natural turnover takes place).
The bottom line is that short-term fluxes (as large as they might be) don’t matter if they are reciprocated by an equivalent but opposite flux. If you want, let’s do the experiment. You pay $1,000 onto my account ever odd week, and I pay $1,000 onto yours every even week. None of us will care – as little as the atmosphere will worry about the carbon that your grass patch briefly locks away from it.
So your grass won’t lock away carbon dioxide from the atmosphere in the long run. Neither will any grassland in New Zealand.
If you wait long enough, things can become a bit more complicated, namely if my payments back to you start to become a little less or a little more, causing dollars or carbon to accumulate on one account rather than the other. While this is the case in some ecosystems, such as a growing forest, New Zealand grassland is unlikely one of them. So your backyard isn’t helping, there is no way around reducing our greenhouse gas emissions.
In evolutionary terms, sea snakes are relative newcomers to aquatic life, having evolved from land-based snakes only about 16 million years ago. This is much more recent than marine mammals such as whales and dugongs, which arose around 50 million years ago.
The roughly 60 known species of sea snakes have nevertheless developed an impressive array of adaptations to marine life. These include salt glands under the tongue, nostrils that face upwards and can be sealed by valves, paddle-like tails to facilitate swimming, and the ability to absorb oxygen and eliminate carbon dioxide through their skin.
Just when we thought we had uncovered all the strange things sea snakes do, we discovered something new. As we report today in the journal Royal Society Open Science, the annulated sea snake Hydrophis cyanocinctus effectively has a set of gills on its forehead.
The first sign of something unusual was an odd hole (in anatomical terms, a “foramen”, the Latin word for “hole”) in the roof of this species’ skull.
This hole is reminiscent of the “pineal foramen” found in several lizard species, which contains a tiny light-sensitive organ called the pineal eye. Could sea snakes also have a pineal eye?
No trace of such a foramen has ever been found in a modern snake. In fact, snakes are thought to have lost the pineal foramen at least 100 million years ago, which is the age of the oldest reasonably complete fossil snakes.
However, because some sea snakes have light-sensitive organs in their tails, we couldn’t rule out the possibility of a light-sensitive organ reappearing in its ancestral position in the skull – snakes did evolve from lizards, after all.
Not an eye, but a lung
We decided to investigate this unexpected foramen in H. cyanocinctus more closely. We obtained some live specimens from Vietnam, where sea snakes are commonly sold as food in fish markets, and generated images of the soft tissues around the foramen using a combination of traditional and computer-assisted methods.
These images revealed that this snake does not have a pineal eye. What actually goes through the mysterious hole in its skull is a large blood vessel (sometimes paired). This blood vessel then travels forward and branches into a complex network of veins and sinuses immediately under the skin of the forehead and snout.
We then examined other snakes, both terrestrial and marine, using the same methods, and realised that this network of blood vessels in H. cyanocinctus is unique.
While a network of blood vessels is expected to be present under the skin of all snakes, what is special about H. cyanocinctus is the greatly exaggerated size of the blood vessels and the fact that they converge towards a single large vein that goes into the brain.
Gills on top of the head
This strange network of blood vessels makes sense when we consider that sea snakes can breathe through their skin. This happens thanks to arteries containing much lower oxygen concentrations than the surrounding seawater, which allows oxygen to diffuse through the skin and into the blood.
However, these low oxygen levels in arterial blood can cause problems, because the brain may not get the oxygen it needs. The dense network of veins on the forehead and snout of these sea snakes helps solve this problem by picking up oxygen from seawater and redistributing it to the brain while swimming underwater.
If you think that sounds similar to what fish do with their gills, you’re absolutely right. H. cyanocinctus has managed to evolve a respiratory system that works in much the same way as gills, despite the vast evolutionary distance between these two groups of species. Truly, these snakes are indeed creatures of the sea.
An article in The Australian recently claimed that on the east coast electric vehicles are responsible for more carbon dioxide emissions than their petrol counterparts.
The findings were largely attributed to Australia’s reliance on coal-fired power to charge electric vehicles. The report on which the article was based has not been publicly released, making it difficult to examine the claim.
Battery electric vehicles have no exhaust emissions. Their emissions are primarily determined by the upstream emissions: that is, from the production and distribution of the energy used to charge them.
In a paper I co-authored late last year, we estimated that the typical Australian petrol vehicle generated 355 grams of CO₂-equivalent per kilometre in real-world fuel life cycle emissions.
By comparison, a typical electric vehicle charged using the average Australian electricity grid mix generated about 40% fewer emissions, at 213 grams of CO₂-equivalent per kilometre.
Even with dirty energy, electric cars are greener
Electric vehicle emissions vary depending on how dirty the region’s electricity is. By applying the 2019 National Greenhouse Accounts Factors to the same methodology used in our journal paper, electric vehicle emissions in each of Australia’s electricity grids were calculated (see Table 1, click to zoom).
Victoria has the most emissions-intensive grid in Australia due to its reliance on brown coal. However, even in that state, the real-world fuel life cycle emissions of a typical electric vehicle would still be 20% lower than a typical petrol vehicle. In Tasmania, which is dominated by renewable energy, electric vehicle emissions would be 88% lower than a comparable petrol vehicle.
Let’s examine four different sized electric vehicles in Australia to see how their fuel lifecycle emissions compare to petrol vehicle equivalents (see Table 2, click to zoom).
Even when large electric cars are charged using Victoria’s grid, emissions are 6-7% lower than a petrol vehicle equivalent.
Using both real-world emissions estimates and Green Vehicle Guide data, the shift from petrol to electric vehicles is shown to deliver a reduction in emissions – no matter where vehicles are charged in Australia (see Table 3, click to zoom).
And of course emissions from electric vehicles will fall further as grid electricity continues to become cleaner.
There is clearly a strong relationship between ownership of both electric vehicles and zero-emission rooftop solar.
In 2018 we surveyed more than 150 electric vehicle owners in Australia (representing 2% of the national fleet). We found that 80% of vehicle charging occurred at home, with 73% of respondents owning rooftop solar systems (compared to an average of 21.6% of homes nationally)).
Additionally, 22% of electric vehicle owners surveyed had stationary battery storage attached to their solar rooftop systems, with another 53% planning to install batteries in the near future.
Five more reasons to embrace electric vehicles:
Cost savings: Electric vehicles are 70-90% cheaper to operate, potentially saving households more than A$2,000 per year.
5) Health benefits: Noxious emissions from traditional vehicles also take a massive toll on our health by contributing to rates of asthma and other chronic illnesses. Vehicle pollution causes an estimated 40% to 60% more premature deaths than road accident fatalities in Australia. Electric vehicles provide a pathway to avoid these deaths.
Even international bank BNP Paribas sees the writing on the wall. In advice to investors last month it outlined that thanks to electric vehicles, the economics of oil for transport was “in relentless and irreversible decline, with far-reaching implications for both policymakers and the oil majors.”
*Note: The Green Vehicle Guide figures in Table 2 are based on a 1997 drive cycle – the New European Drive Cycle or NEDC – which significantly underestimates real-world emissions and efficiency. As a result, Green Vehicle Guide values for all vehicles are lower than the real-world emissions estimates we published in our 2018 paper. Despite this, the relative difference in emissions between electric and petrol vehicles is largely consistent with our estimates – see Table 3 – and therefore these figures are still useful for comparing different vehicles.