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fechar este livroRoots and Tubers for the 21st Century - Trends, Projections, and Policy Options. 2020 Vision for Food, Agriculture, and the Environment. Discussion Paper 31 (IFPRI, 2000, 72 p.)
Ver o documento(introduction...)
Ver o documentoForeword
Ver o documentoAcknowledgments
Ver o documento1. Introduction
Ver o documento2. Trends in the Use of Roots and Tubers
Ver o documento3. Trends in the Supply of Roots and Tubers
Ver o documento4. Baseline Projections of Production and Use
Ver o documento5. High Demand and Production Growth Scenario
Ver o documento6. Roots, Tubers, and the Environment
Ver o documento7. Conclusions and Recommendations
Ver o documentoAppendix: Supplementary Tables
Ver o documentoReferences

5. High Demand and Production Growth Scenario

Past projections for some R&T in developing countries - most notably potato - have often underestimated actual increases in demand and supply (see Scott 1983a). These low projections have resulted from income elasticities of demand based on data from industrialized countries and the assumption that consumers in Africa, Asia, and Latin America will behave in a fashion similar to their developed-world counterparts (Horton 1981). In many cases, they have not. Estimates of actual income elasticities of demand for specific roots and tubers in developing countries are relatively few and far between, which partly accounts for the need to “extrapolate” from the experience of industrialized countries. Furthermore, the estimates that do exist are for particular time periods, often for a subsection of the population (for example, rural households), and invariably for fresh products. Moreover, trends beginning in some cases as early as the 1960s indicate that the structure of demand and supply for R&T in the developing world is undergoing fundamental shifts (Scott and Suarez 1992). As consumption of processed products increases, the small number of estimates for fresh roots and tubers becomes less and less appropriate. If the continued rapid increase in potato demand, for example, particularly in Asia and parts of WANA, is sustained for several more years, the upward shift in income elasticities may be even greater than accounted for in the baseline scenario.

These upward shifts make it necessary to explore a high demand and production growth (HDP) scenario that incorporates a more sustained increase in supply and demand for those developing countries and regions currently experiencing rapid growth in the R&T sector. This chapter examines the impact of this faster supply and demand growth on the regional and global supply/demand situation in 2020.

On the demand side, the HDP scenario incorporates food demand elasticities for potato that are 0.20 higher than in the baseline scenario for Egypt, India, and Turkey and 0.10 higher for China (selected baseline elasticities are given in the Appendix, Table 26). For sweetpotato feed in China the HDP scenario incorporates a higher ratio of sweet-potato per unit of livestock output. And for cassava and other roots and tubers, the HDP scenario uses demand elasticities that are 0.35 higher than in the baseline for Nigeria and central-west Sub-Saharan Africa, and 0.20 higher for the rest of Sub-Saharan Africa. On the supply side, area growth rates for potato are assumed to increase by 0.50 percent per year more than in the baseline scenario for China, Egypt, and India, and by 0.20 percent per year more for Turkey. Yield growth in China is assumed to be 0.70 percent per year above the baseline rate of growth, reflecting more rapid technological change. For cassava and other roots and tubers, area growth for Sub-Saharan Africa is assumed to increase by an additional 0.30 percent per year. The HDP scenario thus incorporates the assumption that the accelerating growth in supply and demand for R&T seen in the early 1990s tapers off more gradually than in the baseline scenario.

HDP Projections for R&T Use

According to the HDP scenario, total use of R&T in developing countries is projected to increase by 74 percent between 1993 and 2020, or an additional 64 million mt compared to the baseline scenario (Tables 8 and 18). More than half of the additional increase (35 million mt) is attributable to faster growth in use of potato, with the remainder roughly evenly divided between cassava and other roots and tubers (16 million mt) and sweetpotato and yam (13 million mt). Average annual increases in total use of potato during 1993-2020 are considerable: 2.8 percent versus 2.0 percent in the baseline scenario. The HDP growth rate for use is more modest for sweetpotato and yam: 1.5 percent per year versus 1.3 percent. Annual growth in the use of cassava and other roots and tubers is estimated at 2.2 percent, versus 1.9 percent in the baseline scenario (Tables 9 and 19). For cassava and potato, these HDP growth rates are still below recent historical trends.

Table 18 - Total use of roots and tubers in 1993, and projections to 2020, HDP scenario


Cassavaa

Potato

Sweetpotato and yamb

All R&T

Country/region

1993

2020

1993

2020

1993

2020

1993

2020


(million metric tons)

China

5.1

7.5

42.7

89.2

108.0

136.8

155.9

233.6

Other East Asia

1.8

1.9

2.6

3.6

0.9

1.1

5.4

6.7

India

5.7

7.4

16.3

44.6

1.2

1.2

23.2

53.3

Other South Asia

0.9

1.4

3.5

7.5

0.5

0.7

4.9

9.5

Southeast Asia

18.9

25.3

1.4

2.7

5.3

7.7

25.6

35.7

Latin America

30.3

43.2

13.0

20.6

2.5

3.5

45.8

67.3

WANA

0.9

1.0

12.8

23.9

0.1

0.2

13.8

25.1

Sub-Saharan Africa

87.7

181.2

2.8

6.3

36.0

77.4

126.4

265.0

Developing

152.0

270.2

95.2

198.6

155.5

229.9

402.7

698.7

Developed

20.7

20.6

190.1

204.8

2.5

2.6

213.3

228.0

World

172.7

290.8

285.3

403.5

158.0

232.5

616.0

926.7

Source:

IMPACT Simulations, June 1998.

Notes:

WANA is West Asia and North Africa. See Table 2 footnote for regional breakdown.

a These figures are for cassava and other roots and tubers such as taro. For developing countries, cassava alone accounts for over 97 percent of the total.

b Estimates for Sub-Saharan Africa are largely for yam, given the roughly 80/20 distribution in favor of yam production in the region, according to FAO 1999a. Estimates for Asia and WANA are for sweetpotato only, and in Latin America estimates are 68/32 for sweetpotato versus yam.

Table 19 - Projected annual growth rates in food, feed, and total use of roots and tubers, 1993-2020, HDP scenario


Cassavaa

Potato

Sweetpotato and yamb

All R&T

Country/region

Food

Feed

Total

Food

Feed

Total

Food

Feed

Total

Food

Feed

Total


(percent per year)

China

0.00

2.77

1.40

2.78

2.74

2.76

-1.03

2.24

0.88

0.22

2.35

1.51

Other East Asia

0.87

0.21

0.11

1.30

1.31

1.26

0.74

1.23

0.74

1.17

1.12

0.81

India

1.01

na

1.01

3.80

na

3.80

0.12

na

0.12

2.99

na

3.13

Other South Asia

2.10

...

1.69

2.90

na

2.89

1.08

...

0.95

2.57

...

2.53

Southeast Asia

1.11

0.91

1.09

2.40

2.38

2.55

1.28

2.25

1.35

1.23

1.40

1.23

Latin America

0.78

1.73

1.33

1.71

1.58

1.71

1.04

1.80

1.24

1.23

1.73

1.44

WANA

1.51

0.42

0.73

2.33

1.56

2.33

1.45

na

1.44

2.31

0.59

2.24

Sub-Saharan Africa

2.80

1.53

2.73

3.15

1.78

3.14

2.93

1.72

2.87

2.83

1.55

2.78

Developing

2.24

1.72

2.15

2.75

2.66

2.76

0.50

2.23

1.46

1.88

2.17

2.06

Developed

-0.52

0.03

-0.03

0.34

0.20

0.28

0.22

0.37

0.23

0.33

0.14

0.25

World

2.23

1.02

1.95

1.39

1.01

1.29

0.49

2.21

1.44

1.49

1.49

1.52

Source:

IMPACT Simulations, June 1998.

Notes:

Ellipses (...) signify very small values; na signifies no recorded use. WANA is West Asia and North Africa. Total use includes food, feed, and other uses. See Table 2 footnote for regional breakdown.

a These figures are for cassava and other roots and tubers such as taro. For developing countries, cassava alone accounts for over 97 percent of the total.

b Estimates for Sub-Saharan Africa are largely for yam, given the roughly 80/20 distribution in favor of yam production in the region, according to FAO 1999a. Estimates for Asia and WANA are for sweetpotato only, and in Latin America estimates are 68/32 for sweetpotato versus yam.

Asian countries, particularly China, will experience the bulk of the additional increase in food and feed demand for potato projected in the HDP scenario. In comparison to the baseline scenario, per capita consumption of potato in 2020 will increase by 3.3 kg to 23 kg in China, by 4.2 kg to 25 kg in India, and by 2.5 kg to 31 kg in WANA (Tables 11 and 20). For South Asia and WANA, where some estimates of expenditure elasticities for potato have been estimated using household survey (Bouis and Scott 1996; Goletti 1993) and time-series data (Fuglie 1994), the HDP increases reflect the available empirical evidence. A combination of field surveys (Ye and Rozelle 1993), marketing and demand studies (Pacific-Vision 1995b; Zhang et al. 1999), and commercial updates (VIPDT 1999) suggest that the higher R&T projections for China in effect do reflect recent trends. In short, a historical perspective shows that the additional per capita food demand for potato projected for Asia by the HDP scenario is a plausible alternative to the baseline.

Table 20 - Per capita use of roots and tubers as food in 1993, and projections to 2020, HDP scenario


Cassavaa

Potato

Sweetpotato and yamb

All R&T

Country/region

1993

2020

1993

2020

1993

2020

1993

2020


(kilograms per year)

China

2

2

14

23

45

28

61

53

Other East Asia

1

1

18

21

6

5

24

27

India

6

6

13

25

1

1

20

32

Other South Asia

3

3

9

11

2

1

13

15

Southeast Asia

32

31

3

3

10

10

45

44

Latin America

25

22

22

24

3

3

50

49

WANA

1

1

28

31

...

...

29

31

Sub-Saharan Africa

131

135

3

3

36

38

169

176

Developing

24

30

13

18

19

15

56

62

Developed

...

...

75

76

1

1

77

77

World

19

24

27

28

15

12

61

65

Source:

IMPACT Simulations, June 1998.

Notes:

Ellipses (...) signify very small values. WANA is West Asia and North Africa. See Table 2 footnote for regional breakdown.

a These figures are for cassava and other roots and tubers such as taro. For developing countries, cassava alone accounts for over 97 percent of the total.

b Estimates for Sub-Saharan Africa are largely for yam, given the roughly 80/20 distribution in favor of yam production in the region, according to FAO 1999a. Estimates for Asia and WANA are for sweetpotato only, and in Latin America estimates are 68/32 for sweetpotato versus yam.

The HDP scenario also indicates a substantial increase in the use of sweetpotato as animal feed in China: 2.2 percent per year during 1993-2020 compared to 1.8 percent per year in the baseline scenario (Tables 9 and 19). The projected slower decline in the world market price of maize over the next 20 years (when compared to Rosegrant, Agcaoili-Sombilla, and Perez 1995, 26) might make sweetpotato a more competitive feed source. Genetic improvements in sweetpotato varieties and improvements in feed preparation at the household and village levels could further boost the use of sweetpotato as feed.

Sub-Saharan Africa will account for nearly all of the additional demand for cassava under the HDP scenario: 13 million mt of the projected total increase of 16 million mt. As a result, per capita food demand for cassava in Sub-Saharan Africa will increase from 131 kg in 1993 to 135 kg in 2020 under the HDP scenario, instead of declining to 124 kg as projected under the baseline scenario (Tables 11 and 20). Total use of sweetpotato and yam in Sub-Saharan Africa in 2020 will increase by 3 million mt compared to the baseline scenario (Tables 8 and 18), and per capita food demand will increase from 36 kg in the baseline scenario to 38 kg under the HDP scenario (Tables 11 and 20).

HDP Projections for Production, Area, and Yield

Annual average growth rates for production of R&T in developing countries during 1993-2020 are higher for all commodities under the HDP scenario compared to the baseline (Tables 13 and 21).

Table 21 - Production levels and annual growth rates of production for roots and tubers, 1993-2020, HDP scenario


Cassavaa

Potato

Sweetpotato and yamb

All R&T


Production

Growth rate

Production

Growth rate

Production

Growth rate

Production

Growth rate

Country/region

1993

2020


1993

2020


1993

2020


1993

2020



(million mt)

(percent/yr)

(million mt)

(percent/yr)

(million mt)

(percent/yr)

(million mt)

(percent/yr)

China

4.8

6.6

1.21

42.5

87.8

2.72

108.5

136.0

0.84

155.8

230.4

1.46

Other East Asia

na

na

na

2.4

3.3

1.18

0.8

1.1

1.36

3.2

4.4

1.22

India

5.8

7.1

0.76

16.3

43.3

3.67

1.2

1.3

0.44

23.3

51.7

3.00

Other South Asia

0.8

1.3

1.61

3.5

7.7

2.98

0.5

0.7

1.27

4.8

9.7

2.62

Southeast Asia

42.0

48.2

0.51

1.3

2.3

2.08

5.3

8.0

1.49

48.6

58.5

0.68

Latin America

30.3

42.0

1.22

12.6

20.2

1.76

2.6

3.7

1.41

45.5

65.9

1.39

WANA

0.1

0.2

1.61

13.0

23.4

2.21

0.1

0.2

1.55

13.3

23.9

2.19

Sub-Saharan Africa

87.8

183.8

2.77

2.6

6.0

3.06

36.0

78.0

2.90

126.4

267.7

2.82

Developing

172.4

290.3

1.95

94.3

194.0

2.71

155.9

230.2

1.45

422.6

714.6

1.96

Developed

0.4

0.4

0.67

191.0

209.5

0.34

2.1

2.3

0.36

193.4

212.2

0.34

World

172.7

290.8

1.95

285.3

403.5

1.29

158.0

232.5

1.44

616.0

926.7

1.52

Source:

IMPACT Simulations, June 1998.

Notes:

na signifies not applicable. WANA is West Asia and North Africa. See Table 2 footnote for regional breakdown.

a These figures are for cassava and other roots and tubers such as taro. For developing countries, cassava alone accounts for over 97 percent of the total.

b Estimates for Sub-Saharan Africa are largely for yam, given the roughly 80/20 distribution in favor of yam production in the region, according to FAO 1999a. Estimates for Asia and WANA are for sweetpotato only, and in Latin America estimates are 68/32 for sweetpotato versus yam.

Table 22 - Area planted and annual growth rates in area planted for roots and tubers, 1993-2020, HDP scenario


Cassavaa

Potato

Sweetpotato and yamb

All R&T


Area

Growth rate

Area

Growth rate

Area

Growth rate

Area

Growth rate

Country/region

1993

2020


1993

2020


1993

2020


1993

2020



(million ha)

(percent/yr)

(million ha)

(percent/yr)

(million ha)

(percent/yr)

(million ha)

(percent/yr)

China

0.3

0.3

0.09

3.1

3.7

0.67

6.2

5.6

-0.36

9.6

9.6

0.02

Other East Asia

na

na

na

0.2

0.2

-0.39


0.1

0.44

0.2

0.2

-0.20

India

0.2

0.2

0.03

1.0

1.6

1.71

0.1

0.1

-0.04

1.4

2.0

1.31

Other South Asia

0.1

0.1

0.22

0.3

0.4

0.92

0.1

0.1

0.22

0.5

0.6

0.71

Southeast Asia

3.5

3.5

0.03

0.1

0.1

0.58

0.8

0.8

0.15

4.4

4.4

0.06

Latin America

2.7

2.7

-0.01

1.0

1.1

0.43

0.3

0.3

-0.10

4.0

4.1

0.09

WANA

...

...

0.12

0.7

0.8

0.67

...

...

0.22

0.7

0.8

0.66

Sub-Saharan Africa

11.9

17.2

1.39

0.4

0.6

1.27

4.2

5.9

1.26

16.5

23.7

1.36

Developing

18.8

24.2

0.94

6.8

8.6

0.84

11.9

13.1

0.35

37.5

45.8

0.74

Developed

...

...

-0.07

11.6

11.0

-0.18

0.1

0.1

0.06

11.7

11.2

-0.17

World

18.8

24.2

0.94

18.4

19.6

0.23

12.0

13.2

0.34

49.2

57.0

0.54

Source:

IMPACT Simulations, June 1998.

Notes:

Ellipses (...) signify very small values; na signifies no recorded production. WANA is West Asia and North Africa; ha stands for hectares. See Table 2 footnote for regional breakdown.

a These figures are for cassava and other roots and tubers such as taro. For developing countries, cassava alone accounts for over 97 percent of the total.

b Estimates for Sub-Saharan Africa are largely for yam, given the roughly 80/20 distribution in favor of yam production in the region, according to FAO 1999a. Estimates for Asia and WANA are for sweetpotato only, and in Latin America estimates are 68/32 for sweetpotato versus yam.

Table 23 - Yields and annual growth rates in yield for roots and tubers, 1993-2020, HDP scenario


Cassavaa

Potato

Sweetpotato and yamb

All R&T


Yield

Growth rate

Yield

Growth rate

Yield

Growth rate

Growth rate

Country/region

1993

2020


1993

2020


1993

2020




(mt/ha)

(percent/yr)

(mt/ha)

(percent/yr)

(mt/ha)

(percent/yr)

(percent/yr)

China

15.1

20.3

1.12

13.7

23.7

2.04

17.5

24.2

1.20

1.44

Other East Asia

na

na

na

13.2

20.2

1.57

15.9

20.4

0.92

1.43

India

23.6

28.7

0.73

15.6

26.3

1.94

8.4

9.6

0.48

1.66

Other South Asia

9.4

13.7

1.39

10.9

18.8

2.05

9.1

12.1

1.05

1.89

Southeast Asia

12.1

13.8

0.49

12.5

18.7

1.49

6.8

9.7

1.34

0.62

Latin America

11.3

15.7

1.23

12.9

18.5

1.33

7.6

11.4

1.51

1.29

WANA

32.5c

48.6c

1.50

18.6c

28.1c

1.53

17.8

25.4

1.33

1.53

Sub-Saharan Africa

7.4

10.7

1.36

6.5

10.5

1.77

8.6

13.2

1.62

1.44

Developing

9.2

12.0

1.00

13.8

22.7

1.85

13.1

17.6

1.10

1.21

Developed

12.1

14.8

0.74

16.5

19.0

0.52

17.9

19.4

0.30

0.52

World

9.2

12.0

1.00

15.5

20.6

1.06

13.2

17.6

1.09

0.98

Source:

IMPACT Simulations, June 1998.

Notes:

na signifies no recorded production. WANA is West Asia and North Africa, ha stands for hectares. See Table 2 footnote for regional breakdown.

a These figures are for cassava and other roots and tubers such as taro. For developing countries, cassava alone accounts for over 97 percent of the total.

b Estimates for Sub-Saharan Africa are largely for yam, given the roughly 80/20 distribution in favor of yam production in the region, according to FAO 1999a. Estimates for Asia and WANA are for sweetpotato only, and in Latin America estimates are 68/32 for sweetpotato versus yam.

c FAO indicates very high yields in Egypt on small areas.

For developing counties as a whole, total root and tuber production under the HDP scenario is projected to expand at 2.0 percent per year between 1993 and 2020. This figure is about 20 percent higher than the annual growth rate of 1.6 percent projected by FAO for the period 1988/90-2010 (Alexandratos 1995), but just below the recent historical growth rate of 2.1 percent (Table 5).

According to the HDP scenario, the largest increase in production of R&T in Asia will be for potato and sweetpotato. Almost 80 percent of the additional potato output of 32 million mt in developing countries, compared to the baseline scenario, will be harvested in China (24 million mt) and 19 percent in India (6 million mt) (Tables 13 and 21). The difference between HDP and baseline production in China and India results from additional area planted and a larger increase in average yields (Tables 14 and 22 and 15 and 23). As robust as the potato area and production growth rates for China and India appear, the HDP projections constitute a slowdown in recent trends. Chinese production, for example, drops from an annual growth rate of 4.6 percent per year for 1983-96 (Table 5) to 2.7 percent per year for 1993-2020 (Table 21).

The additional production of sweetpotato in China of almost 8 million mt by 2020 under the HDP scenario will account for nearly all of the increase in Asia and for more than 60 percent of the increase for all developing countries (Tables 13 and 21). This added output will be used largely for animal feed. The higher production of sweetpotato and yam will result mostly from increases in yield. Area planted with sweetpotato and yam is projected to decline by 0.6 million hectares between 1993 and 2020 (Table 22). The higher yields for sweetpotato in China (Table 23) can well materialize through greater use of improved germplasm bred specifically for use as feed. China has considerable potential for yield improvement because it has had limited access to improved germplasm for sweetpotato. Davis and Ryan (1987) estimated that benefits from investments in sweetpotato research in China would outweigh those for any of the other 22 commodities they studied, except for rice, wheat, and potato. The relatively higher feed demand projected for sweetpotato under the HDP scenario could accelerate investments in this crop as growers seek out yield-increasing technology and cost-reducing procurement, processing, and feeding practices linked to specific postharvest uses, such as pork production.

Sub-Saharan Africa will account for practically all the additional output of cassava. The 15 million mt difference between HDP and baseline cassava production in Sub-Saharan Africa in 2020 will come from an additional 1.3 million hectares under cultivation and a slight increase in yield (Tables 14 and 22 and 15 and 23). Annual growth in area will increase to 1.4 percent from 1.1 percent under the baseline scenario.

It might be argued that the projected increase in area planted to R&T will be limited by disappearing agricultural frontiers and limits to the cropping index (the ratio of crop area harvested to arable land). This would affect Sub-Saharan Africa the most because some 7 million of the estimated 8 million hectare expansion of R&T area in developing countries is projected to take place in that region during 1993-2020. However, the overall projected increase in area planted to R&T is insignificant when compared to the 3.3 billion hectares of potential land area available for crop production, not to mention possible further intensification of the cropping index (Rosegrant et al. 1997).

HDP Projections for World Prices and International Trade

The faster growth scenario for R&T means that R&T prices will decline more slowly to 2020 (Table 16). On average, world prices for R&T will fall by 12 percent under the HDP scenario, instead of by 19 percent. The more modest price declines reflect the stronger demand, particularly for sweet-potato as feed in China. The HDP scenario has only minor effects on the commodity composition and volume of R&T trade.

The level of net exports of cassava and other roots and tubers by developing countries increases only slightly (by 81,000 mt), but the mix of importers and exporters changes. China switches from being a net exporter to a net importer. Net exports of cassava by Sub-Saharan Africa rise fivefold to 2.6 million mt.14 China's altered trade position suggests that feed demand simply outpaces feed supply given the prices generated by the HDP scenario. In contrast, the more abundant supply of cassava and other roots and tubers in Sub-Saharan Africa facilitates exports from that region. A similar situation arises in the case of sweetpotato and yam for China and Sub-Saharan Africa.

14 These absolute figures for net exports should be interpreted with caution given that they represent only a small percentage of total output and use.

Net imports of potatoes by developing countries jump from 1.2 million mt under the baseline scenario to 4.6 million mt under the HDP scenario as China, India, and WANA switch from being net exporters to net importers. Strong demand in developing countries under the HDP scenario generates greater imports of processed potato products from Europe and North America. Overall, however, international trade will remain a minor share of developing-country production of R&T and will continue to be highly skewed toward cassava and Southeast Asia under the HDP scenario.15

15 These trade estimates must be interpreted with caution given uncertainties about the accuracy of the published trade data (see for example, Scott, Basay, and Maldonado 1997).

The Value of R&T Production Under the HDP Scenario

The more robust demand and production growth rates and the resulting higher prices under the HDP scenario lead to a larger value for R&T production in 2020. Under the HDP scenario, the share of R&T in the total value of the major food crops plus soybean and selected meat commodities remains at 10.5 percent, the share R&T contributed in 1993. R&T's share in the value of crop production (that is cereals, soybean, and R&T), however, increases from 16.7 percent in 1993 to 18.6 percent in 2020 (Table 17). In terms of individual commodities, potato's share in the total value of major foods rises to 4.9 percent in 2020 from 4.1 percent in 1993. Yam also increases its value share, but sweetpotato declines in relative importance. Cassava and other R&T slip in value, but by an insignificant amount (Table 17). The bulk of the increase in R&T value is located in Asia and Sub-Saharan Africa. The value of R&T in Latin America declines in relative importance across all commodities.

To summarize, although the HDP growth rates for supply and demand of R&T are notably higher than those in the baseline scenario, they reflect recent accelerating trends in output and use, particularly in the cases of potato and yam.

Both scenarios project that the largest absolute increase in R&T production by 2020 will take place in Sub-Saharan Africa. China will account for the bulk of the projected sweetpotato output. China and India together will harvest between 62 percent (baseline) and 68 percent (HDP) of the future supply of potatoes in developing countries. Cassava production will expand the most - by 80-100 million mt - in Sub-Saharan Africa. The projected expansion in area planted falls well within the range available for crop cultivation, even after taking into account area expansion for the other major food crops.

Increases in R&T production will be driven by demand for food in the cases of potato (both fresh and processed) and yam. The demand for feed and starch (in both food and industrial products) will be met mostly by cassava and sweetpotato.

In the baseline scenario R&T will decline in economic importance vis-a-vis the other major food commodities over the next two decades, though the decline relative to other food and feed crops will be marginal. Under the HDP scenario, the economic importance of R&T will either remain unchanged or, in the case of food and feed crops, increase slightly. This latter finding contrasts with earlier projections that estimated significant declines in the importance of R&T (see, for example, Alexandratos 1995; McCalla 1998).