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Short communication

Climatic growing conditions of Jatropha curcas L.

W.H. Maesa, A. Trabuccoa,b, W.M.J. Achtena, B. Muysa,*aKatholieke Universiteit Leuven, Division Forest, Nature and Landscape, Celestijnenlaan 200 E Box 2411, BE-3001 Leuven, BelgiumbInternational Water Management Institute (IWMI), P.O. Box 2075, Colombo, Sri Lanka

a r t i c l e i n f o

Article history:

Received 5 November 2008

Received in revised form

4 June 2009

Accepted 9 June 2009

Published online 8 July 2009

Keywords:

Biofuel

climate

ecological niche

Physic nut

aridity index

length of growing season

length of drought period

* Corresponding author. Tel.: þ32 16 329726;E-mail address: bart.muys@ees.kuleuven

0961-9534/$ – see front matter ª 2009 Elsevidoi:10.1016/j.biombioe.2009.06.001

a b s t r a c t

The massive investment in new jatropha plantations worldwide is not sufficiently based on

a profound scientific knowledge of its ecology. In this article, we define the climatic

conditions in its area of natural distribution by combining the locations of herbarium

specimens with corresponding climatic information, and compare these conditions with

those in 83 jatropha plantations worldwide.

Most specimens (87%) were found in tropical savannah and monsoon climates (Am, Aw)

and in temperate climates without dry season and with hot summer (Cfa), while very few

were found in semi-arid (BS) and none in arid climates (BW). Ninety-five percent of the

specimens grew in areas with a mean annual rainfall above 944 mm year�1 and an average

minimum temperature of the coldest month (Tmin) above 10.5 �C. The mean annual

temperature range was 19.3–27.2 �C.

The climatic conditions at the plantations were different from those of the natural

distribution specimens for all studied climatic variables, except average maximum

temperature in the warmest month. Roughly 40% of the plantations were situated in

regions with a drier climate than in 95% of the area of the herbarium specimens, and 28% of

the plantations were situated in areas with Tmin below 10.5 �C.

The observed precipitation preferences indicate that jatropha is not common in regions

with arid and semi-arid climates. Plantations in arid and semi-arid areas hold the risk of

low productivity or irrigation requirement. Plantations in regions with frost risk hold the

risk of damage due to frost.

ª 2009 Elsevier Ltd. All rights reserved.

1. Introduction investors and community project developers all over the

Jatropha curcas L. is a perennial, deciduous, stem-succulent

shrub [1], which produces seeds rich in oil easily convertible

into biodiesel meeting international standards [2]. With its

ability to reclaim degraded and/or dry lands with potentially

positive impact on biodiversity and soil resources [3], jatropha

takes a special place among the biofuel crops and is currently

conquering the hearts of many governments, private

fax: þ32 16 329760..be (B. Muys).er Ltd. All rights reserved

tropical world [4]. However, these major claims rest on

a narrow scientific base [5–7], and the hyped interest might

hold the risk of unsustainable practices [8]. The main knowl-

edge gaps are situated in the cultivation part, mainly

concerning water requirements [8,9], growth and yield

response to input [3,5–7].

Several authors mention biophysical limits of the species

[1,6,10], but provide data based on generalizations of scattered

.

b i o m a s s a n d b i o e n e r g y 3 3 ( 2 0 0 9 ) 1 4 8 1 – 1 4 8 51482

observations, rather than on systematic research. Yet this

knowledge is crucial, as jatropha should still be considered

a wild and undomesticated plant showing great variability in

productivity between individual plants [3].

In this article, we aimed to define the climatic conditions of

jatropha in its area of natural distribution and to compare

these with the climatic conditions in plantations, combining

information on locations of herbarium specimens and plan-

tations with regionalized climate data.

2. Materials and methods

There is general agreement that the original area of distribu-

tion of jatropha is Mexico and continental Central America

(Belize, Costa Rica, El Salvador, Guatemala, Honduras,

Nicaragua and Panama) (e.g. Refs. [10–14]). Although still

controversial, in this article we considered these countries as

the regions where jatropha is a native species.

2.1. Data collection

The World Biodiversity Information Network [15] contains

information on 241 herbarium specimens of jatropha

collected in Mexico and continental Central America. The

specimen locations were used to derive information on the

growing conditions of the species in its natural area of

distribution. Furthermore, the locations of 83 current jatropha

plantations worldwide were collected through extensive

internet search and personal contacts. These sample loca-

tions were overlaid with the bioclimatic WorldClim geo-

dataset [16] and a Koppen-Geiger climate classification map

[17], having a pixel size of, respectively, 1 and 10 km at the

equator.

Of the 19 bioclimatic variables available from WorldClim,

the mean annual precipitation (Pa [mm]), the mean annual

temperature (Tmean), mean minimum daily temperature of the

coldest month (Tmin) and mean maximum daily temperature

of the warmest month (Tmax – all in �C) were selected [18] and

calculated for each sample location.

Potential evapotranspiration (PET), calculated with the

Hargreaves Method [19], Aridity Index (AI [/] – the ratio of

mean annual precipitation to total PET [20]) and the length

of the growing season (LGS [# months year�1] – the number of

months in which the mean precipitation is higher than half of

the PET [21]) were calculated for each location.

A global spatially distributed soil water balance model was

applied with monthly PET and monthly precipitation as input

and assuming average soil hydraulic conditions and a refer-

ence crop (extensive surface of actively growing green grass of

uniform height (0.12 m), cf. [22]) as the standard vegetation

[23], thus calculating the potential available water (PAW – the

amount of soil water currently available to the reference crop

expressed as a proportion of the maximum amount of plant

available water the soil can hold). Months with a PAW value

below 0.37, an average threshold value for diverging stomatal

conductance [24], were considered as drought months. The

length of the drought period (LDP [# months year�1]) was then

estimated for each specimen or plantation location as the

longest continuous period of months in which the reference

crop would suffer from drought.

Of each variable, the mean, 25th and 75th percentile (to

estimate the optimal range for this variable) were calculated

of the locations of natural distribution and of the plantations

separately. For the estimation of the total range, the 5th and

95th percentiles were used to exclude possible extreme values

due to incorrectness of the overlay of points with WorldClim

maps. The total range derived from the specimens in the

natural area of distribution is further denoted as the natural

range.

2.2. Statistical analysis

To compare the environmental conditions of the natural

distribution sites with the plantation sites, the nonparametric

Mann–Whitney test was used for each variable separately, due

to absence of normality and homogeneity of variance between

groups. All testing was performed using SPSS 15.0 (SPSS Inc.,

Chicago, IL).

3. Results

The location of the jatropha specimens in the area of natural

distribution is given in Fig. 1. For each climate type where

jatropha was found, the relative area in the natural area of

distribution and the relative number of herbarium and plan-

tation locations (all in %) are given in Table 1.

Of the natural area of distribution, 25% and 9% have

a tropical savannah climate (Aw) and a tropical monsoon

climate type (Am), respectively, while 53% and 27% of the

specimens were located in areas with these climate types.

In total, 84.7% of the herbarium specimens were found in

regions with tropical climates (Af, Am and Aw). Furthermore,

regions with temperate climates without dry season and with

hot (Cfa) or warm (Cfb) summer cover 2.4% of the natural area,

while 7.4% of the specimens were found in areas with these

climates. Jatropha specimens were not present to a great

extent in temperate climates with dry winter (Cwa, Cwb).

Moreover, 27% of the area of natural distribution has a hot or

cold steppe climate (or semi-arid climate), while only 2.5% of

the specimens were found in this climate type. No specimens

were found in regions with arid climates, which cover 16%

of the area.

All derived environmental variables and statistical test

results are given in Table 2.

Compared with the specimens’ locations, plantations were

relatively less situated in tropical climates (A) and relatively

more in temperate (C), arid (BW) and semi-arid (BS) climates

(Table 1), and the environmental conditions of the natural

distribution and the plantations were different for all

measured variables except for Tmax. In 28% of the plantations,

Tmin was lower than that of the 5th percentile of

the herbarium specimens, 10.5 �C. Similarly, roughly 40% of

the plantations were situated in areas drier than those in the

natural area (Pa, AI and LGS below the 5th percentile of the

natural distribution, and LDP above the 95th percentile).

Thirty-nine percent of the plantation sites were inside the

natural range for both Tmin and the drought variables.

Fig. 1 – Location of the J. curcas specimens in its area of natural distribution, in which the different climate zones

(after Peel et al. [17]) are drawn.

b i o m a s s a n d b i o e n e r g y 3 3 ( 2 0 0 9 ) 1 4 8 1 – 1 4 8 5 1483

4. Discussion

The use of presence-only data such as herbarium specimens

can cause two kinds of bias: a regional bias because not all

sites/climates were sampled alike and a bias towards more rare

species [25]. The large number and regional spread of jatropha

specimens together with the large total number of herbarium

records in the area (the WBIN dataset counts 1,380,000 records

in the studied area) reduce both kinds of bias.

The natural ranges given in Table 2 do not necessarily

reflect the true biophysical limits, i.e. the total ranges of the

fundamental niche (the subset of n-dimensional environ-

mental space of all possible conditions in which a species can

maintain itself in the absence of distribution limitations or

interspecific competition), but rather the total ranges of the

Table 1 – The relative area in the natural area of distribution and(all in %) of the climate types where J. curcas was found (see Fi

Tropical climates (A) A

Af Am Aw BWh

Natural distribution area 6.3 9 25.5 14.6

Specimen locations 4.6 27.4 52.7 0

Plantation locations 3.7 1.2 45.7 6.2

realized niche (the subset of the fundamental niche where

a species is present) [26]. In plantations, where distributional

limitations are obviously of no concern and where competi-

tion with other species for water, nutrients and light is

limited, jatropha can probably survive and grow in more

extreme conditions. Nevertheless, although not true for every

species, realized niches are usually centered around the

region where a species performs optimally [26].

The results demonstrate that jatropha is not common in

regions with arid and semi-arid climates and does not naturally

occur in regions with Pa of less than 944 mm year�1. This

contrasts with popular claims on preferred climate (e.g. Refs.

[10,27]) and with the limiting rainfall levels stated in recent

literature, ranging from 200 mm [28] to 300 mm [11], yet agrees

well with the observation that production in sites with

900–1200 mm rainfall can be up to double (5 t dry seed ha�1 yr�1)

the relative number of herbarium and plantation locationsg. 1 for the definition of the climate symbols used).

rid and semi-aridclimates (B)

Temperate climates (C)

BSh BSk Cwa Cwb Cfa Cfb

15.6 11.4 8.3 5.1 1.7 0.7

2.5 0 3.3 2.1 6.6 0.8

12.3 1.2 14.8 7.4 7.4 0

Table 2 – Mean, optimal range (25–75% percentiles) and total range (5–95% percentiles) of all considered climate variables forthe locations of the area of natural distribution of J. curcas (n [ 241), the mean, total range of the plantation locations(n [ 83) and percentage of plantation locations outside the total range of the natural distribution area, and the P value of theMann–Whitney test.

Statistic Tmean,�C

Tmin,�C

Tmax,�C

Pa,mm year�1

LGS,# of months

LDP,# of months

AI,/

Specimen locations

Mean 24.4 16.5 32.5 1689 7.3 2.2 1.04

Optimal range 23.4–26.2 14.4–19.4 31.5–34.0 1207–2001 6–9 0–4 0.73–1.19

Total range 19.3–27.2 10.5–21.2 27.4–35.7 944–3121 5–11 0–5 0.55–1.99

Plantation locations

Mean 23.5 12.7 33.3 1064 5.7 4.3 0.64

Total range 17.2–27.7 4.4–19.3 27.6–41.6 440–1757 1–12 0–10 0.24–1.18

% Below/above

natural range

7.2/9.6 27.7/3.6 3.6/25.3 43.4/0 34.9/6.0 0/37.3 44.6/0

% Outside

natural range

16.9 31.3 28.9 43.4 41 37.3 44.6

P (Mann–Whitney) 0.008 <0.001 0.58 <0.001 <0.001 <0.001 <0.001

b i o m a s s a n d b i o e n e r g y 3 3 ( 2 0 0 9 ) 1 4 8 1 – 1 4 8 51484

of the production in semi-arid regions (2–3 t dry seed ha�1 yr�1)

[3,7]. It indicates that plantations in arid or semi-arid regions

(19.5% of the sampled plantations in this study) may show a low

productivity or need additional irrigation.

While Tmin of the realized niche was much higher than

7 �C, considered as a boundary temperature below which frost

can occur [29], 11% of the plantations were situated in areas

with Tmin below 7 �C. Jatropha is frost sensitive and sheds its

leaves immediately after frost [30,31]. Although it can recover

from slight frost [10], seed production will be very low [30] and

plants die after more severe frost [31]. Given the tendency of

the natural range towards warmer climatic conditions with

longer return periods of damaging frost events, this is an

underestimated risk.

The Tmean of the natural sites agrees well with data cited in

the literature (e.g. Ref. [10]: 20–28 �C) and the plantations were

planted in regions with comparable Tmean.

In conclusion, the natural climatic conditions of jatropha

are more humid and have a higher Tmin than its commonly

believed site requirements, and therefore point towards

cautious selection of plantation sites.

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