doesn't removal of fertile topsoil and replacement of it with rocks and cacti at scale actually reduce carbon sequestration and heat absorption capacity?
Plus, mowing a lawn is usually done with some of the dirtiest engines out there.
Removing lawns is always a net good.
i understand the notion of returning to existing vegetation, but these places are already irreversibly altered by the presence of humans anyway. buildings and parking lots and roads and sidewalks have been built.
it's pretty striking when you see what little soil remains being replaced with rocks.
And yes, xeriscaping is striking. Absolutely beautiful to see native plants, well adapted to the climate, thriving and taking center stage.
The heat absorption is a good point, I don't know what native foliage is like to live in compared to the concrete hell you'd be left with without lawns. But, I find it hard to imagine that turf grass in climates where it can't survive without massive irrigation and ceaseless human intervention sequesters more carbon than it costs to maintain.
The numbers I've quickly gathered are all over the place, but given that:
- The average Californian lawn is ~500 sqm [0]
- Grass sequesters ~ 85g of carbon per sqm per year, or 42 tonnes per year [1]
- As of 2011 the average Californian household uses 190 gallons of potable water a day on landscaping [2]
- About 0.004 metric tonnes of carbon is generated processing 1000 gallons of potable water or 0.76 tonnes per day of watering [3]
So, the average Californian lawn sequesters 42 tonnes of carbon a year, while the energy cost of irrigating it emits about 277 tonnes.
This is all quick back of an envelope math, but the carbon cost of irrigating a lawn where it wasn't meant to grow is massively larger than the amount that the grass sequesters. It's honestly bad enough that you could tear up every lawn in California and not even bother replacing them with native foliage, and it would still result in a net decrease in carbon emissions.
[0]: https://www.homeadvisor.com/r/average-yard-size-by-state/
[1]: https://www.researchgate.net/publication/282543110_Modeling_...
[2]: https://www.kqed.org/lowdown/11525/how-much-water-do-califor...
[3]: http://leansixsigmaenvironment.org/index.php/how-much-impact...
> - Grass sequesters ~ 85g of carbon per sqm per year, or 42 tonnes per year [1]
500 * 85g/m2 = 42500 g/m2 - that's 42.5 kg, not 42.5 tonnes.
I haven't checked your original sources, but based on the numbers you provided you're off by 3 orders of magnitude. Intuitively this makes sense, I mean 42 tonnes is a huge amount of carbon to sequester in a lawn. Where would all that mass go? It would mean that the average lawn produces >> 42 tonnes of grass per year.
500 sqm X 85 g/yr is 42.5 kg/yr
Also, 190 gpd / 1000 gal = 0.19 kgal per day
0.004 tons per kgal per day x 0.19 x 365 days = .277 tons per year
Therefore 0.0425 tons sequestered, 0.277 tons produced by irrigation.
The ratio of carbon sequestered to carbon produced on irrigation is the same as your original calculations.
But I think the major source of carbon won't be in irrigation, but in the maintenance, mowing the lawn, transportation for the landscaper, transporting pesticides and fertilizers, etc.
here's a thought experiment: assume infinite clean electricity and desalination capacity in the face of an overcarbonated atmosphere and climate change. do you install and irrigate as much vegetation as you can or do you rip it all out and put in rocks?
Here's some stats
https://www.pressdemocrat.com/article/specialsections/these-...