6 ms·

so here's a fun question: it's become quite trendy in policy circles in california to incentivize the removal of lawns and gardens as part of water conservation

by a-dub 4y ago

so here's a fun question: it's become quite trendy in policy circles in california to incentivize the removal of lawns and gardens as part of water conservation efforts. doesn't removal of fertile topsoil and replacement of it with rocks and cacti at scale actually reduce carbon sequestration and heat absorption capacity?

halfmatthalfcat 4y ago
The water conservation need outweighs the marginal carbon sequestration I’d imagine.
Victerius 4y ago
What was the vegetation like before humans arrived? We should go back to that.
ceejayoz 4y ago
Grassy lawns and lush gardens in dry areas require so much water any water any possible benefit of carbon sequestration is counterbalanced by the irrigation infrastructure required.
- 0des 4y ago
  Do cashew farms and strawberries next
  - piva00 4y ago
    As far as I know almonds are a major water-guzzler of Californian crops, no?
    - djbusby 4y ago
      Yep Here's some stats https://www.pressdemocrat.com/article/specialsections/these-are-the-california-crops-that-use-the-most-water/ https://www.pressdemocrat.com/article/specialsections/these-...
turtledove 4y ago
I don't think so in any meaningful way. Also, removing and wasting the water to keep a lawn green heats the river that water was pulled from. Plus, mowing a lawn is usually done with some of the dirtiest engines out there. Removing lawns is always a net good.
- a-dub 4y ago
  sure, but don't we put lawns on roofs in cities to try and cool them down in the summer? 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.
  - turtledove 4y ago
    Rooftop lawns in cities are to offset the increase in heat generated by having the city there. They are an attempt to return the environment to something closer to natural. And yes, xeriscaping is striking. Absolutely beautiful to see native plants, well adapted to the climate, thriving and taking center stage.
  - pickovven 4y ago
    In many places green roofs are primarily about reducing rainwater runoff, which causes pollution. However in hot areas like LA, they also reduce building temperatures which reduces energy consumption. Lawns don't reduce building temperatures.
iandinwoodie 4y ago
In addition, I wonder what effect this sort of “manual desertification” has on the soil when done en masse.
- Majestic121 4y ago
  It seems odd to me to frame this as manual desertification. Isn't it the opposite, return to a natural state after manual "grassification" that requires strong human intervention?
- turtledove 4y ago
  It's not an environment that naturally supports soil. The energy and water needs to support an unnatural environment are quite large.
DoughnutHole 4y ago
[EDIT: Below I have demonstrated a slow brain rot that has robbed me of my ability to do basic dimensional analysis. My lecturers are spinning in their graves, least of all because I forgot that the kilogram is between the gram and the tonne. Luckily I was off by 3 orders of magnitude in both directions so I guess it sort of balances out?] 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/ https://www.homeadvisor.com/r/average-yard-size-by-state/ [1]: https://www.researchgate.net/publication/282543110_Modeling_Carbon_Sequestration_in_Home_Lawns https://www.researchgate.net/publication/282543110_Modeling_... [2]: https://www.kqed.org/lowdown/11525/how-much-water-do-californians-use-and-what-would-20-percent-less-look-like https://www.kqed.org/lowdown/11525/how-much-water-do-califor... [3]: http://leansixsigmaenvironment.org/index.php/how-much-impact-does-one-gallon-of-water-in-your-home-or-business-have-on-the-environment/ http://leansixsigmaenvironment.org/index.php/how-much-impact...
- leto_ii 4y ago
  > - The average Californian lawn is ~500 sqm [0] > - 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.
titzer 4y ago
Most of LA would be a rocky semi-desert without irrigation. If you want to sequester carbon, maybe do it someplace that does have rainfall to support an effective carbon-sink ecosystem and doesn't require huge amounts of energy input?
- ianai 4y ago
  I wonder if there’s some vegetation that could be watered with seawater and take the place of grass? Places like LA have plenty of that, seemingly.
lobocinza 4y ago
Lawn is net zero if you ignore all secondary emissions because the grass will be cut and decompose into methane. When the many secondary emissions are considered it's certainly emitting more carbon than it capture. But it improve the micro-climate of the city and possibly reduce AC usage.

by a-dub 4y ago

halfmatthalfcat 4y ago

The water conservation need outweighs the marginal carbon sequestration I’d imagine.

Victerius 4y ago

What was the vegetation like before humans arrived? We should go back to that.

ceejayoz 4y ago

Grassy lawns and lush gardens in dry areas require so much water any water any possible benefit of carbon sequestration is counterbalanced by the irrigation infrastructure required.

0des 4y ago
Do cashew farms and strawberries next
- piva00 4y ago
  As far as I know almonds are a major water-guzzler of Californian crops, no?
  - djbusby 4y ago
    Yep Here's some stats https://www.pressdemocrat.com/article/specialsections/these-are-the-california-crops-that-use-the-most-water/ https://www.pressdemocrat.com/article/specialsections/these-...

turtledove 4y ago

I don't think so in any meaningful way. Also, removing and wasting the water to keep a lawn green heats the river that water was pulled from. Plus, mowing a lawn is usually done with some of the dirtiest engines out there. Removing lawns is always a net good.

a-dub 4y ago
sure, but don't we put lawns on roofs in cities to try and cool them down in the summer? 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.
- turtledove 4y ago
  Rooftop lawns in cities are to offset the increase in heat generated by having the city there. They are an attempt to return the environment to something closer to natural. And yes, xeriscaping is striking. Absolutely beautiful to see native plants, well adapted to the climate, thriving and taking center stage.
- pickovven 4y ago
  In many places green roofs are primarily about reducing rainwater runoff, which causes pollution. However in hot areas like LA, they also reduce building temperatures which reduces energy consumption. Lawns don't reduce building temperatures.

iandinwoodie 4y ago

In addition, I wonder what effect this sort of “manual desertification” has on the soil when done en masse.

Majestic121 4y ago
It seems odd to me to frame this as manual desertification. Isn't it the opposite, return to a natural state after manual "grassification" that requires strong human intervention?
turtledove 4y ago
It's not an environment that naturally supports soil. The energy and water needs to support an unnatural environment are quite large.

DoughnutHole 4y ago

[EDIT: Below I have demonstrated a slow brain rot that has robbed me of my ability to do basic dimensional analysis. My lecturers are spinning in their graves, least of all because I forgot that the kilogram is between the gram and the tonne. Luckily I was off by 3 orders of magnitude in both directions so I guess it sort of balances out?] 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/ https://www.homeadvisor.com/r/average-yard-size-by-state/ [1]: https://www.researchgate.net/publication/282543110_Modeling_Carbon_Sequestration_in_Home_Lawns https://www.researchgate.net/publication/282543110_Modeling_... [2]: https://www.kqed.org/lowdown/11525/how-much-water-do-californians-use-and-what-would-20-percent-less-look-like https://www.kqed.org/lowdown/11525/how-much-water-do-califor... [3]: http://leansixsigmaenvironment.org/index.php/how-much-impact-does-one-gallon-of-water-in-your-home-or-business-have-on-the-environment/ http://leansixsigmaenvironment.org/index.php/how-much-impact...

leto_ii 4y ago
> - The average Californian lawn is ~500 sqm [0] > - 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.

titzer 4y ago

Most of LA would be a rocky semi-desert without irrigation. If you want to sequester carbon, maybe do it someplace that does have rainfall to support an effective carbon-sink ecosystem and doesn't require huge amounts of energy input?

ianai 4y ago
I wonder if there’s some vegetation that could be watered with seawater and take the place of grass? Places like LA have plenty of that, seemingly.

lobocinza 4y ago

Lawn is net zero if you ignore all secondary emissions because the grass will be cut and decompose into methane. When the many secondary emissions are considered it's certainly emitting more carbon than it capture. But it improve the micro-climate of the city and possibly reduce AC usage.