[MCN] Locally grown veggies best re climate? Maybe, or maybe not

[Lance Olsen]

How does your garden grow?
UCSB research professor David Cleveland and his students model the 
effect of household gardens on greenhouse gas emissions
UNIVERSITY OF CALIFORNIA - SANTA BARBARA
PUBLIC RELEASE: 7-SEP-2016

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"It's important not to get hung up on assumptions that small and 
local are always better," Cleveland said. "They may not be. You have 
to keep your eye on the real goal and not get tripped up by 
intermediate steps.

"This study shows that in terms of effect on the climate, small 
things matter," he added. "How much attention you pay to the garden 
matters. How efficiently the vegetables are produced and consumed 
matters."
=====================

Turning lawn into a vegetable garden can reduce greenhouse gas 
emissions, according to a new study by UC Santa Barbara research 
professor David Cleveland.

Using a lifecycle assessment model, Cleveland and his students 
demonstrated that greenhouse gas emissions can be cut by 2 kilograms 
for every kilo of homegrown vegetable when compared to the 
store-bought counterpart. The group's findings appear in the journal 
Landscape and Urban Planning.

For their baseline scenario, the researchers modeled a vegetable 
garden based on converting an area of lawn to garden, replacing some 
conventionally produced purchased vegetables with ones from the 
garden and diverting some household organic waste and gray water from 
processing facilities for use as compost and water for the garden.

The researchers chose midrange numbers from the wide range of values 
in the existing data. They also conducted a sensitivity analysis to 
test how key components such as crop yield and managing organic 
affected the model.

"We looked at high and low yields and found that they affected the 
emissions per kilogram of vegetable," Cleveland explained. "For every 
square meter of garden, if you get 10 times the amount of vegetables, 
then the amount of emissions per vegetable goes down, because you're 
dividing more vegetables into the emissions per square meter. 
Ironically, that makes the contribution of the garden less on a 
per-vegetable basis. This means for the garden as a whole, higher 
yield reduces the emissions because fewer vegetables are purchased."

Another variable also impacted outcomes: the way in which household 
organic waste was handled. "There's the potential for home composting 
to be either positive or negative for the climate," Cleveland said. 
"It takes a lot of attention to do it right." He noted that if 
optimal moisture and air conditions are not maintained, the waste 
becomes anaerobic and emits methane and nitrous oxide, powerful 
greenhouse gases.

"We found that if household organic waste was exported to landfills 
that captured methane and burned it to generate electricity, 
households sending their organic waste to a central facility would 
reduce greenhouse gas emissions more than composting at home," 
Cleveland said.

"This study shows that in terms of effect on the climate, small 
things matter," he added. "How much attention you pay to the garden 
matters. How efficiently the vegetables are produced and consumed 
matters."

Cleveland noted that composting often requires more time and 
attention than people are willing to give. At UCSB, the Associated 
Students Department of Public Worms (DPW) is helping to make the 
campus aware of how to compost efficiently. They turn food scraps 
from campus dining commons into compost for the Campus Edible 
Program. In any given month, DPW collects up to 4,000 pounds of 
pre-consumer compostable waste to feed worms in each of its 
8-by-4-foot bins.

However, according to Cleveland, it might be better for many 
household or community gardeners to lobby for good centralized 
programs for organic waste management. The equipment and energy 
necessary to operate such an endeavor constitute a small portion of 
the total emissions. These could be offset by efficiency such as 
having the trucks that come to pick up organic waste also deliver 
compost to people who want it for their gardens.

"It's important not to get hung up on assumptions that small and 
local are always better," Cleveland said. "They may not be. You have 
to keep your eye on the real goal and not get tripped up by 
intermediate steps."

The researchers also calculated the potential contribution of 
vegetable gardens to official climate change mitigation targets for 
reductions of greenhouse gas emissions per year. In the baseline 
scenario, they found that the gardens contributed 0.5 percent of the 
city of Santa Barbara's 2050 target, 3.3 percent of the 2020 target 
for unincorporated Santa Barbara County and 7.8 percent of the state 
of California's 2020 target
.
"In addition to reducing greenhouse gas emissions, there are other 
potential environmental, social, psychological and nutritional 
advantages to growing food yourself, whether in a household, 
community or school garden," Cleveland said. "However, the degree to 
which those benefits are realized can depend on small things. Our 
hope is that this research helps motivate households, communities and 
policymakers to support vegetable gardens that can contribute to 
mitigating climate change."
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"This study informs debate in the literature regarding whether these 
increasingly large fires are 'ecological catastrophes.' 
Landscape-scale severe burning was catastrophic from a tree overstory 
perspective, but from an understory perspective, burning promoted 
rich and productive native understories, despite the entire 10-year 
postfire period receiving below-average precipitation."

SCOTT R. ABELLA and PAULA J. FORNWALT. Ten years of vegetation 
assembly after a North American mega fire. Global Change Biology 
(2014), doi: 10.1111/gcb.12722
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"A surprising result is the high proportion of species responding to 
recent, relatively mild climate change (global average warming of 0.6 
C)."

Camille Parmesan. "Ecological and Evolutionary Responses to Recent 
Climate Change." Annual Review of Ecol. Evol. & Systematics  2006. 
37:637-69






















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