Agriculture
| Author | Peter H. Lehner and Nathan A. Rosenberg |
| Pages | 772-822 |
Page 772 Legal Pathways to Deep Decarbonization in the United States
I. Introduction
Agriculture is both a source and a sink for greenhouse
gases. To convey agriculture’s contribution to climate
change accurately, this chapter focuses on net emissions—
that is, the quantity of greenhouse ga ses released into the
atmosphere less the quantity sequestered in soil and plants.
Decisionmakers can ta ke full advantage of agriculture’s
potential to slow climate change only by acknowledging
the sector’s dual role in decarbonizing the economy, and
seeking both to minim ize agricultural greenhouse gas
emissions and to maximi ze carbon storage.
Two terms are used throughout this chapter to describe
agricultural met hods that reduce net agricultural emis-
sions. e rst, “climate-friendly,” refers to practices or
strategies that reduce greenhouse ga s emissions or increase
soil carbon sequestration when compared to conventional
methods. While superior to standa rd practices, climate-
friendly practices are not necessa rily optimal, both in
terms of their climate benets or their overall benet to
society. In contrast, “carbon farming” describes a suite
of climate-friendly practices and strategies designed to
result in optimal environmental, societa l, and climate out-
comes.1 For example, anaerobic digesters, which reduce
greenhouse gas emissions from concentrated animal feed-
ing operations (CAFOs), may be climate friendly, but
they do not fall under the chapter’s denition of carbon
farming because t hey are integrated into a system of agri-
cultural production with signicant greenhouse gas emis-
1. “Carbon farming” includes grazing and animal husbandry. As Eric Toens-
meier notes in e Carbon Farming Solution, there are “several, sometimes
conicting, denitions of carbon farming.” However, it is generally de-
scribed as a system of agricultural economics and practices organized around
carbon sequestration. E T, T C F S
6 (Brianne Goodspeed & Laura Jorstad eds., 2016). “Regenerative agri-
culture” is another term for largely overlapping agricultural practices. See
generally R I, R O A
C C.
Chapter 30
Agriculture
by Peter H. Lehner and Nathan A. Rosenberg
Summary
is chapter examines the agricultural strategies, practices, and technologies available to increase soil carbon
sequestration and reduce GHG emissions. It summarizes the research documenting the many agricultural prac-
tices that have been demonstrated to reduce GHG emissions and increase carbon sequestration in soil, including
cover cropping, more varied crop rotations, agroforestry and silvopasture (adding trees into cropping or grazing
systems), perennial crops, prescribed rotational grazing, dr y manure management, and others. It details path-
ways for amending existing federal and state legal regimes and enacting new ones, and recommends improving
public agricultural research, development, and extension eorts; reforming federal subsidy and conservation pro-
grams; and revising trade policy, tax policy, regulatory strategies, nancing for carbon farming, g razing practices
on government land, and GHG pricing. It also describes how the private and philanthropic sectors can stimulate
carbon farming; strategies for reducing emissions that stem from farm inputs and that result from food pro-
cessing, distribution, consumption, and waste; and the potential to encourage consumption of climate-friendly
foods through national dietary guidelines, procurement at all levels of government, and private-sector initiatives
such as certication schemes and healthier menu options. e chapter notes that many of the practices recom-
mended to reduce agriculture’s contribution to climate change also will make farms a nd ranches more resilient
to extreme weather and often increase soil health, productivity, and protability. ere can thus be a conuence
of interests supporting incentives for broader adoption of these practices.
Page 773
sions (especially from feed production) and other negative
environmental externalities.
While not applicable in the absence of an economy-
wide price on carbon, there is a further di erence between
climate-friendly practices and carbon farming: the for-
mer focuses on the production of agricultural goods
while reducing greenhouse gas emissions; the latter views
increased carbon soil sequestration as a goal. As discu ssed
below, the United States now uses hundreds of millions
of acres of land to grow crops that are largely wasted or
used ineciently to produce corn ethanol, sweeteners, or
highly processed an imal products. With a price on carbon,
soil carbon sequestration could become one of the primar y
uses of this land, while farmers would be compensated for
sequestering practices. e result could be a signicant
increase in the carbon sink .
Decisionmakers should prioritize climate-friendly prac-
tices that reinforce carbon farming systems. A lthough
many Republican leaders, as well a s rural voters, tend
to ignore or doubt climate science, the many benets of
climate-friendly practices provide independent reasons for
their adoption. Althou gh not the norm currently—and
not widely supported by agrochemical companies and
other traditional sources of information— climate-friendly
practices almost always improve soil health and thus can
increase farm yield, enha nce resilience to climate change,
and often increase protability (especially over the longer
term). us, decisionmakers, regardless of their position
on climate change, should strongly support broader adop-
tion of these practices to assist fa rmers, ranchers, and rural
communities, and to protect basic environmental needs
such as clean air and water.
is chapter focuses on agricultural emissions because
agriculture presents a unique and complex set of chal lenges
and opportunities. Nonetheless , to aid readers in de velop-
ing a comprehensive understanding of possible and neces-
sary emissions reductions, the chapter a lso briey addresses
avenues to reduce emissions from other components of the
food system, discussed in det ail elsewhere.
Section II discusses a griculture’s role in deep decarbon-
ization. It also examines the on-eld strategies, practices,
and technologies available to increase soil ca rbon seques-
tration and reduce agricultura l emissions. (Fisheries and
aquaculture are also important parts of the food system
but, as they present very dierent greenhouse gas a nd legal
issues, they are not addressed in t his chapter.)
Section III details public law pathways —amending
existing federal a nd state legal regimes a nd enacting new
ones—for reducing net agricultural emissions. It begins
by identifying pathways for improving public agricul-
tural research, development, and extension eorts, and
then considers opportunities to reform federal subsidy and
conservation programs. e section also evaluates trade
policy, tax policy, regulatory strategies, nancing for car-
bon farming, grazing practices on government land, and
greenhous e gas pricing.
Section IV describes non-public law approaches, focus-
ing on how the private and philanthropic sectors can
stimulate carbon farm ing. e topics covered include agri-
cultural resea rch, nancing for carbon farming, measu ring
carbon content, conservation tools, and oset markets.
Section V looks at overall food system emissions. It
provides an overview of strategies for reducing upstream
emissions—those that stem f rom farm inputs—and down-
stream emissions—t hose that result from food processing,
distribution, consumption, and waste.
Finally, Section VI examines the potential to encour-
age the consumption of climate-friendly foods throug h
national dietary guidelines, procurement at all levels of
government, as well as through private-sector initiatives,
such as certication schemes and healthier menu options.
Section VII concludes.
II. Agriculture’s Role in Deep
Decarbonization
A. Greenhouse Gas Emissions in the Food System
e food system encompasses the full life cycle of food.
In addition to agriculture, this includes activities that take
place o the farm—from the pre-planting conversion of
native grasslands a nd production of agricultura l chemicals,
for example, to the post-harvest distribution, consump-
tion, and disposal of food.2 e food system is responsible
for an estimated 19%-29% of both national and global
greenhous e gas emissions. 3 Decisionmakers must approach
the food system as a whole to craft laws and policies that
address the system’s full complement of social, nutritional,
and environmental i mpacts.
2. Sonja Vermeulen et al., Climate Change and Food Systems, 37 A. R.
E’ R 195, 198-202 (2012).
3. Id. at 195. GRAIN, an international research and advocacy organization,
estimates that emissions from the food system are as high as 44%-57%
of global emissions. GRAIN, Commentary IV: Food, Climate Change, and
Healthy Soils: e Forgotten Link, in T E R
2013, at 19-20 (United Nations Conference on Trade and Development
2013).
Page 774 Legal Pathways to Deep Decarbonization in the United States
B. Reducing Net Emissions From Agriculture
Agriculture refers to the cultivation of crops and the rais-
ing of animals for the “4Fs”: food, feed, fuel, and ber. It
accounts for 51% of the country’s total landmass a nd 61%
of the landmass of the contiguous 48 states, making it the
single largest ty pe of land use in the United States.4 Of the
country’s total 2.3 billion acres, approximately 408 million
acres are in use as cropland, 614 million acres as grassland
pasture and range, a nd 127 million acres as grazed for-
estland.5 As a result of agriculture’s large footprint, rela-
tively small changes in agricultura l practices, which may
have a modest impact per acre, can signic antly aect this
sector’s contribution to climate change if they are widely
implemented. Small changes can a lso improve farmers’
and ranchers’ ability to adapt to the changing climate.
A core concept of this chapter is that carbon seques-
tration should be added to this list of the funda mental
aims of agriculture, a s well as to the federal programs
and policies that support it. Achieving climate stability
is as critical a human need a s the other functions of agri-
culture. By reducing greenhouse gas emissions while also
increasing soil carbon stores, agricultural operations can
make a substantial contribution to decarbonization in
the United States.
1. Greenhouse Gas Emissions From
Agriculture
e U.S. Environmental Protection Agency (EPA) esti-
mates that emissions from agricultu re account for approx-
imately 9% of total U.S. greenhouse gas emissions each
yea r.6 Unlike the energy a nd transportation sectors, which
emit primarily carbon dioxide as fossil fuels are burned,
crop and livestock greenhouse gas emissions consist
largely of nitrous oxide and methane. Nitrous oxide is a
particularly potent greenhouse ga s—the average radiative
forcing of nitrous oxide is 265-298 times that of carbon
dioxide over 100 years.7 Nitrous oxide emissions will also
be the primary cause of stratospheric ozone destruction
this century.8 Like nitrous oxide, methane is a powerful
greenhouse gas: the average radiative forcing of methane is
about 28-34 times that of carbon dioxide over 100 years.
4. C N ., U.S. D A, M
U L U S, 2007, at 4 (2011) (EIB-89).
5. Id.
6. EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks, https://www.
epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks
(last updated Apr. 12, 2018).
7. I P C C, C C
2013: T P S B 714 (2014). Table 8-7 presents these
and other “global warming potential” values.
8. A.R. Ravishankara et al., Nitrous Oxide (N2O): e Dominant Ozone-Deplet-
ing Substance Emitted in the 21st Century, 326 S 123, 123-25 (2009).
In 2016, total agricultural emissions of nitrous oxide
and methane amounted to about 560 million metric tons
of carbon dioxide equivalent.9 In other words, agriculture
released an amount of greenhouse ga ses roughly equivalent
to that produced by 120 million automobiles in a typi-
cal yea r.10 Agriculture is responsible for more than 80%
of U.S. nitrous oxide emissions and almost 40% of U.S.
methane em issions.11
As Figure 1 shows, the largest source of U.S. agricul-
tural greenhouse ga s emissions is agricultural soil man-
agement—a series of practices intended to improve crop
yields, including fertilization, tillage, drainage, irrigation,
and fal lowing of l and.12 Soil management generates hal f
of all U.S. agricultura l emissions and 94% of all U.S.
nitrous oxide emissions from agriculture.13 Seventy-three
percent of nitrous oxide emissions from agricultural soil
management come from cropland and 27% come from
grazed grasslands.14
e next largest source of agricu ltural emissions is
enteric fermentation, which results from the digestive pro-
9. EPA, I U.S. G G E S: 1990-
2016, at 5-1 (2018) (EPA 430-R18-003).
10. Compare id. with EPA, G G E F T P-
V (2014) (a typical passenger vehicle emits 4.7 metric tons of
carbon dioxide annually).
11. See EPA, Overview of Greenhouse Gases: Nitrous Oxide Emissions, https://
www.epa.gov/ghgemissions/overview-greenhouse-gases#nitrous-oxide
(last updated Apr. 11, 2018); EPA, Overview of Greenhouse Gases: Meth-
ane Emissions, https://www.epa.gov/ghgemissions/overview-greenhouse-
gases#methane (last updated Apr. 11, 2018).
12. EPA, supra note 9, at 5-21, 5-22. Soil emits nitrous oxide in a dynamic pro-
cess involving a number of factors, including humidity and precipitation,
in addition to soil management practices. See Klaus Butterbach-Bahl et al.,
Nitrous Oxide Emissions From Soils: How Well Do We Understand the Processes
and eir Controls?, 368 P. T R S’ B (2013). Till-
age and unrestricted grazing also disturb existing soil carbon content stores,
resulting in carbon loss.
13. See EPA, supra note 9, at 5-2 tbl. 5-1.
14. See id. at 5-26 tbl. 5-17.
Soil Management
Enteric Fermentation
Manure Management
Rice Cultivation
Urea Fertilization
Liming
Field Burning
283.6
170. 1
85.8
0.4
13.7
5.1 3.9
Figure 1
Major Sources of Agricultural Emissions
in the United States
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