Impacts on Plant Pathogens - Climate Resilient Agriculture for Ensuring Food Security - page 164

current and future climates. This approach was
used by Sansford and Baker ( 1998 ) to assess the
risk of establishment of Karnal bunt in the cereal-
growing regions of the European Union.
Exclusion of pathogens and quarantines
through regulatory means may become more dif-
fi cult for authorities as unexpected pathogens
might appear more frequently on imported crops.

rule for the presence or absence of the disease
based on long-term means of temperature and
precipitation. This rule was then implemented in
a climate-matching program to identify high-risk
regions in Africa, Australia, Latin America, and
Southeast Asia under current climate. Further,
two climate change scenarios were run for loca-
tions in Southeast Asia. The results suggested an
increase in disease risk in Northern Vietnam,
Southern Laos, and Eastern Thailand. These pre-
dictions are consistent with limited fi eld observa-
tions indicating that severe disease can occur in
these regions during years with extreme weather.
Possible effects of climate change on
Phytophthora cinnamomi , a soilborne oomycete
with an extremely wide host range, were consid-
ered by Brasier ( 1996 ) and Brasier and Scott
( 1994 ). This pathogen requires warm, wet soils
and is hence limited primarily to tropical and
subtropical regions (Lonsdale and Gibbs 1996 ).
More recently, P. cinnamomi has been associated
with oak declines in Southern and Mediterranean
Europe. It was hypothesized (Brasier 1992 ) that
this may be an early indication of climate warm-
ing as the pathogen may have become more
active because of higher soil temperatures and/or
increased host susceptibility caused by stress
(e.g., more frequent winter droughts in the
region). For a more formal impact assessment,
Brasier and Scott ( 1994 ) used the CLIMEX
climate-matching program (Sutherst and
Maywald 1985 ) to map regions in Europe favor-
able or unfavorable for this pathogen under pres-
ent and future climate scenarios. The climate
change simulations suggested that the pathogen
could extend its range further north, although it
appeared unlikely that it could become estab-
lished in those regions where winter temperatures
are low such as Central and Eastern Europe
(Brasier 1996 ). It was further hypothesized that
the pathogen's host range could increase if spread
occurs into regions where it is currently absent.

8.9 Impact Models

Quantitative (modeling) approaches, which allow
one to investigate multiple scenarios and interac-
tions simultaneously, will become more impor-
tant for impact assessment (Coakley and Scherm
1996 ). Guidelines for such model-based assess-
ments are needed, and Sutherst et al. ( 1996 ) and
Teng and Yang ( 1993 ) have given a framework.

8.9.1 Climate Matching

Climate matching involves the calculation of a
“match index” to quantify the similarity in cli-
mate between two or more locations. The match
index is based on variables such as monthly mini-
mum and maximum temperatures, precipitation,
and evaporation. Software packages for climate
matching include BIOCLIM (Busby 1991 ),
HABITAT (Walker and Cocks 1991 ), or CLIMEX
(Sutherst and Maywald 1985 ) and WORLD
(Booth 1990 ). These packages often come with
additional useful features such as internal algo-
rithms for generating “climate surfaces” through
interpolation between stations. Climate matching
may be used for climate change impact assess-
ment by identifying those locations on the globe
with a current climate that is most similar to the
predicted future climate at the location of inter-
est. An analysis of the plant disease problems at
the matching locations, for example, based on
disease distribution maps (Weltzien 1972 ), would
allow predictions to be made about future disease
risk at the location of interest.
Booth et al. ( 2000 ) used climate matching to
identify regions suitable for Cylindrocladium leaf
blight on Eucalyptus spp. in Southeast Asia and

8.9.2 Empirical Models

Four diseases of two major crops in China, wheat
and rice, were examined by regression analysis to