Estimated Land Area Increase of Estimated Land Area Increase of Agricultural Ecosystems to Agricultural Ecosystems to

Sequester Excess Atmospheric Sequester Excess Atmospheric Carbon DioxideCarbon Dioxide

Estimated Land Area Increase of Estimated Land Area Increase of Agricultural Ecosystems to Agricultural Ecosystems to

Sequester Excess Atmospheric Sequester Excess Atmospheric Carbon DioxideCarbon Dioxide

D.G. Wright, R.W. Mullen,

W.E. Thomason, and W.R. Raun

D.G. Wright, R.W. Mullen,

W.E. Thomason, and W.R. Raun

IntroductionIntroductionIntroductionIntroduction The concentration of CO2 in the atmosphere is

increasing by 1.5-2.0 ppm per year, giving rise to an approximate 0.5ºC increase in global temperature (Wittwer, 1985; Perry, 1983).

Keeling and Whorf (1998), report an increase in atmospheric CO2 concentration from 280 ppm to a present level of 365 ppm over the past 60 years.

Approximately 3.3 Pg C (3.3 GT) is added to the atmosphere each year from numerous natural and anthropogenic processes (Follett and McConkey, 2000).

The concentration of CO2 in the atmosphere is increasing by 1.5-2.0 ppm per year, giving rise to an approximate 0.5ºC increase in global temperature (Wittwer, 1985; Perry, 1983).

Keeling and Whorf (1998), report an increase in atmospheric CO2 concentration from 280 ppm to a present level of 365 ppm over the past 60 years.

Approximately 3.3 Pg C (3.3 GT) is added to the atmosphere each year from numerous natural and anthropogenic processes (Follett and McConkey, 2000).

To offset atmospheric accumulation of CO2

and global warming, the conversion of land to agroforestry, rangeland, and no-till/minimum till cropping systems has been identified.

Many scientists believe that agriculture can have the greatest impact in reducing atmospheric C due to our ability to intensively manage agriculture over long periods of time.

To offset atmospheric accumulation of CO2

and global warming, the conversion of land to agroforestry, rangeland, and no-till/minimum till cropping systems has been identified.

Many scientists believe that agriculture can have the greatest impact in reducing atmospheric C due to our ability to intensively manage agriculture over long periods of time.

IntroductionIntroductionIntroductionIntroduction

Increasing land area in agricultural production that sequesters greater concentrations of CO2

appears to be an environmentally friendly means for decreasing atmospheric C.

At this stage in earth’s history, it is believed that mankind can make strides to decrease the current excess C accumulation in the atmosphere.

Increasing land area in agricultural production that sequesters greater concentrations of CO2

appears to be an environmentally friendly means for decreasing atmospheric C.

At this stage in earth’s history, it is believed that mankind can make strides to decrease the current excess C accumulation in the atmosphere.

IntroductionIntroductionIntroductionIntroduction

ObjectivesObjectivesObjectivesObjectives

The objective of this work was to estimate the amount of area required to annually sequester the 3.3 Pg C excess by three different cropping systems (maize, rice, or wheat), temperate forest, or temperate rangeland ecosystems.

The objective of this work was to estimate the amount of area required to annually sequester the 3.3 Pg C excess by three different cropping systems (maize, rice, or wheat), temperate forest, or temperate rangeland ecosystems.

ResultsResultsResultsResults

This approach uses the mean harvest index and percent C in plant biomass along with average global crop yield.

This approach uses the mean harvest index and percent C in plant biomass along with average global crop yield.

MaizeMaize RiceRice WheatWheat

  

ComponentComponent ValueValue

Reference/ Reference/ calculationcalculation ValueValue

Reference/ Reference/ calculationcalculation ValueValue

Reference/ Reference/ calculationcalculation

Average global Average global yield in 1999yield in 1999

4.32 Mg ha4.32 Mg ha-1-1 FAO, 2000FAO, 2000 3.84 Mg ha3.84 Mg ha--

11

FAO, 2000FAO, 2000 2.73 Mg ha2.73 Mg ha--

11 FAO, 2000FAO, 2000

Harvest indexHarvest index 50%50% Sinclair, 1998; Sinclair, 1998; Dale and Dale and Drennan, 1997Drennan, 1997

50%50% Sinclair, 1998Sinclair, 1998 50%50% Slafer et al., Slafer et al., 19991999

Total biomass per Total biomass per hectarehectare

8.64 Mg ha8.64 Mg ha-1-1 4.32 Mg maize 4.32 Mg maize haha-1 -1 * 0.5 * 0.5 (harvest index(harvest index

7.68 Mg ha7.68 Mg ha--

11 3.84 Mg maize ha3.84 Mg maize ha--

11 * 0.5 (harvest * 0.5 (harvest index)index)

5.46 Mg ha5.46 Mg ha--

11 2.73 Mg maize 2.73 Mg maize haha-1-1 * 0.5 * 0.5 (harvest index)(harvest index)

Percent C in Percent C in biomassbiomass

50%50% Fischer and Fischer and Turner, 1978Turner, 1978

50%50% Fischer and Fischer and Turner, 1978Turner, 1978

50%50% Fischer and Fischer and Turner, 1978Turner, 1978

Total C in Total C in biomass per biomass per hectarehectare

4.32 Mg ha4.32 Mg ha-1-1 8.64 Mg maize 8.64 Mg maize haha-1 -1 ** 0.5 (%C)0.5 (%C)

3.84 Mg ha3.84 Mg ha--

11

7.68 Mg maize ha7.68 Mg maize ha--

11 * 0.5 (%C) * 0.5 (%C)2.73 Mg ha2.73 Mg ha--

11 5.46 Mg maize 5.46 Mg maize haha-1-1 * 0.5 (%C) * 0.5 (%C)

Total atmospheric Total atmospheric C excessC excess

---------------------------------------------------------------------------------- 3.3 x 103.3 x 1099 MgMg

Follett and Follett and McConkey, 2000McConkey, 2000

--------------------------------------------------------------------------------

Area required to Area required to sequester excess sequester excess CC

7.6 x 107.6 x 1088 haha

3.3 x 103.3 x 1099 Mg Mg C/4.32 Mg C haC/4.32 Mg C ha--

11

8.59 x 108.59 x 1088 haha

3.3 x 103.3 x 1099 Mg Mg C/3.84 Mg C haC/3.84 Mg C ha--

1.2 x 101.2 x 1099 ha ha 3.3 x 103.3 x 1099 Mg Mg C/2.73 Mg C C/2.73 Mg C haha-1-1

1999 global land 1999 global land area in productionarea in production

1.4 x 101.4 x 1088 ha ha FAO, 2000FAO, 2000 1.53 x 101.53 x 1088 haha

FAO, 2000FAO, 2000 2.14 x 102.14 x 1088 ha ha FAO, 2000FAO, 2000

Estimated percent Estimated percent increase in global increase in global production to production to sequester excess sequester excess COCO

22

543%543% (7.6 x 10(7.6 x 1088 ha/1.4 x 10ha/1.4 x 1088 ha) ha) * 100* 100

561%561% (8.59 x 10(8.59 x 1088 ha/1.53 x 10ha/1.53 x 1088 ha) * ha) * 100100

561%561% (1.2 x 10(1.2 x 1099 ha/2.14 x 10ha/2.14 x 1088 ha) * 100ha) * 100

TABLE 1. Components for calculating global land area increase to sequester excess CO2 TABLE 1. Components for calculating global land area increase to sequester excess CO2

ComponentComponent ValueValue Reference and/or calculationReference and/or calculation

Temperate forest ecosystemTemperate forest ecosystem

Mean net primary productivity of Mean net primary productivity of temperate forests per hectaretemperate forests per hectare

6.7 Mg C ha6.7 Mg C ha-1-1 yr yr-1-1 Amthor et al., 1998Amthor et al., 1998

Total annual excess atmospheric CTotal annual excess atmospheric C 3.3 x 103.3 x 1099 Mg Mg Follett and McConkey, 2000Follett and McConkey, 2000

Area required to sequester excess COArea required to sequester excess CO22 4.93 x 104.93 x 1088 ha ha 3.3 x 103.3 x 1099 Mg C yr Mg C yr-1-1/6.7 Mg C ha/6.7 Mg C ha-1-1 yr yr-1-1

Global land area currently under Global land area currently under temperate foresttemperate forest

7.5 x 107.5 x 1088 ha ha Amthor et al., 1998Amthor et al., 1998

Estimated increase in global temperate Estimated increase in global temperate forest area to sequester excess COforest area to sequester excess CO22

66%66% (4.93 x 10(4.93 x 1088 ha /7.5 x 10 ha /7.5 x 1088 ha) * 100 ha) * 100

Temperate rangeland ecosystemTemperate rangeland ecosystem

Mean net primary productivity of Mean net primary productivity of temperate rangeland per hectaretemperate rangeland per hectare

3.5 Mg C ha3.5 Mg C ha-1-1 yr yr-1-1 Amthor et al., 1998Amthor et al., 1998

Total annual excess atmospheric CTotal annual excess atmospheric C 3.3 x 103.3 x 1099 Mg Mg Follett and McConkey, 2000Follett and McConkey, 2000

Area required to sequester excess COArea required to sequester excess CO22 9.43 x 109.43 x 1088 ha ha 3.3 x 103.3 x 1099 Mg C yr Mg C yr-1-1/3.5 Mg C ha/3.5 Mg C ha-1-1 yr yr-1-1

Global land area currently under Global land area currently under temperate rangelandtemperate rangeland

1.25 x 101.25 x 1099 ha ha Amthor et al., 1998Amthor et al., 1998

Estimated increase in global temperate Estimated increase in global temperate rangeland to sequester excess COrangeland to sequester excess CO22

75%75% (9.43 x 10(9.43 x 1088 ha/1.25 x 10 ha/1.25 x 1099 ha) * 100 ha) * 100

TABLE 2. Components used for calculating the global land area increase of temperate forest and rangeland ecosystems to sequester excess atmospheric CO2 using net primary productivity of ecosystems from Amthor et

al. (1998) data.

TABLE 2. Components used for calculating the global land area increase of temperate forest and rangeland ecosystems to sequester excess atmospheric CO2 using net primary productivity of ecosystems from Amthor et

al. (1998) data.

DiscussionDiscussionDiscussionDiscussion

Although the calculations are simple and the estimates ignore numerous other factors, the areas computed provide a relative idea of the impracticality of agricultural land conversion to reduce atmospheric C.

Transforming land into agricultural ecosystems cannot be viewed as a plausible solution to combat global warming.

Although the calculations are simple and the estimates ignore numerous other factors, the areas computed provide a relative idea of the impracticality of agricultural land conversion to reduce atmospheric C.

Transforming land into agricultural ecosystems cannot be viewed as a plausible solution to combat global warming.

DiscussionDiscussionDiscussionDiscussion

The environmental impacts associated with expanding global agriculture would be increased fossil fuel consumption, a rise in methane emission from rice paddies and NOx from grassland

ecosystems, and a decrease in soil organic matter.

The environmental impacts associated with expanding global agriculture would be increased fossil fuel consumption, a rise in methane emission from rice paddies and NOx from grassland

ecosystems, and a decrease in soil organic matter.

ConclusionConclusionConclusionConclusion The conversion of land into agricultural ecosystems could

improve the sequestration of atmospheric C; however, the effectiveness of this practice would be marginal due to the enormous land area conversion required to assimilate the 3.3 Pg of atmospheric C accumulating annually

Of the ecosystems evaluated in this work, temperate

forests sequester more C per year (6.7-7.1 Mg C ha-1 yr-1) and require the smallest net global increase in land area (an addition of 4.6-4.9 x 108 ha) when compared to other systems.

The conversion of land into agricultural ecosystems could improve the sequestration of atmospheric C; however, the effectiveness of this practice would be marginal due to the enormous land area conversion required to assimilate the 3.3 Pg of atmospheric C accumulating annually

Of the ecosystems evaluated in this work, temperate

forests sequester more C per year (6.7-7.1 Mg C ha-1 yr-1) and require the smallest net global increase in land area (an addition of 4.6-4.9 x 108 ha) when compared to other systems.

To realize the area calculated, land unsuitable for agriculture would likely have to be utilized.

Furthermore, large volumes of natural and economic resources would be consumed in order to implement agricultural production in the areas needed to reduce the atmospheric CO2 level.

To realize the area calculated, land unsuitable for agriculture would likely have to be utilized.

Furthermore, large volumes of natural and economic resources would be consumed in order to implement agricultural production in the areas needed to reduce the atmospheric CO2 level.

ConclusionConclusionConclusionConclusion

Can Organic Carbon be increased? No-till management practices (10 yrs no-tillage with corn,

OC in surface 30 cm increased by 0.25% (Blevins et al. 1983).

N rates in excess of that required for maximum yields result in increased biomass production (decreased harvest index values e.g., unit grain produced per unit dry matter) .

Importance of Organic Carbon For thousands of years, organic matter levels were allowed

to increase in these native prairie soils since no cultivation was ever employed.

As soil organic matter levels declined, so too has soil productivity while surface soil erosion losses have increased. Because of this, net mineralization of soil organic nitrogen fell below that needed for sustained grain crop production (Doran and Smith, 1987).

Can Organic Carbon be increased? No-till management practices (10 yrs no-tillage with corn,

OC in surface 30 cm increased by 0.25% (Blevins et al. 1983).

N rates in excess of that required for maximum yields result in increased biomass production (decreased harvest index values e.g., unit grain produced per unit dry matter) .

Importance of Organic Carbon For thousands of years, organic matter levels were allowed

to increase in these native prairie soils since no cultivation was ever employed.

As soil organic matter levels declined, so too has soil productivity while surface soil erosion losses have increased. Because of this, net mineralization of soil organic nitrogen fell below that needed for sustained grain crop production (Doran and Smith, 1987).