Agriculture Reference
In-Depth Information
6.3.2 DISCUSSION
From a purely GHG emissions perspective, the payback period of four
years or less for Scenario 1 (Table 6) suggests that leaving ∆rA as uncon-
sumed perennial growth was the best GHG mitigation option. While this
benefit would require the elimination of livestock, Scenario 1 could be
used to grow feedstock for cellulosic ethanol [46], or simply be set aside
for environmental purposes like wildlife habitat. With payback periods
at three quarters or less of the 40 year window, Scenario 2 represents a
net gain in CO
2
mitigation potential in the west. In the east, Scenario 2
was neutral with respect to the 40 year payback window. While Scenario
2 eliminated livestock, the annual crops in this scenario would increase
global food supply. Scenario 3 in the west was the only case where re-
populating ∆rA with beef cattle led to a net gain in GHG mitigation po-
tential based on the payback period being less than 40 years. Scenario 3
also had a slight advantage over Scenario 2 in the west. This was because
beef production conserves soil carbon stock and it is a lower input system
than field crops. Due to the heavy dependence on silage corn, this GHG
mitigation benefit was lost in the eastern beef industry under Scenario 3.
Scenario 4 was the least promising mitigation option, in spite of lower
losses of soil carbon than under Scenario 3. This was particularly true in
the east where the net annual GHG emissions actually increased.
The need to apply four scenarios to the basic beef to pork redistribu-
tion is consistent with previous studies involving the interaction between
the beef industry and biofuel feedstock production [5,46]. Like the inter-
action with pork production in this study, these previous studies showed
that displacement of beef with several types of biofuel feedstock has a
range of outcomes depending on how the operators of the displaced beef
farms respond. Similarly, whether or not the residual land in this analysis
will be used sustainably depends largely on how much the beef farm op-
erators will be allowed to share in the economic benefi ts of the land use
shifts [46].
Because the beef to pork redistribution required land to be shifted from
forage to annual grain crops, it was assumed that a suffi cient portion (up to
10%) of the land under forage would be suitable for growing feed grains.
Scenario 2 required that all of ∆rA be suitable for either cereal or pulse
