Miguel F.Acevedo
ABSTRACTS
ASSESSING POTENTIAL IMPACTS OF CO2- AND DEFORESTATION- INDUCED CLIMATE
CHANGE ON MAIZE AND BLACK BEAN IN VENEZUELA
Ecotropicos 8(1-2):39-52. 1995
Miguel F. Acevedo 1,2, Ramon Jaimez 2,3, Carlos E. Maytin 4, Giorgio
Tonella
2, Mark A. Harwell 5
1 Institute of Applied Sciences and Department of Geography, University
of North Texas, Denton TX 76203, USA. 2 Centro de Investigacion y
Proyectos
en Simulacion y Modelos (CESIMO), Facultad de Ingenieria, Universidad
de
Los Andes, Merida 5101, Venezuela. 3 Instituto de Investigaciones
Agropecuarias,
Facultad de Ciencias Forestales, Universidad de Los Andes, Merida 5101,
Venezuela. 4 Centro de Investigaciones Ecologicas de los Andes
Tropicales
(CIELAT), Facultad de Ciencias, Universidad de Los Andes, Merida 5101,
Venezuela. Now at: HIDROANDES, Barinas, Venezuela 5 Rosenstiel School
of
Marine and Atmospheric Science, University of Miami, Miami FL, 33149,
USA.
Abstract
We summarize the potential impacts of climate change on the yield of
maize
(Zea mayz) and black bean (Phaseolus vulgaris L.) at
important
agricultural sites in Venezuela. The effects of greenhouse-induced
global-scale
climatic changes and deforestation-induced continental-scale climatic
changes
were analyzed for both staple crops. The enhanced greenhouse climate
scenarios
(GH) were derived from atmospheric General Circulation Models for
doubled
CO2 conditions. GH scenarios of three levels of sensitivity were
defined
(low, medium and high) from the lower and upper bounds of GCM-derived
temperature
projections. These GH scenarios assume increased air temperature for
both
the wet and dry season and increased rainfall and decreased incoming
solar
radiation for the wet season. Direct effects of increased atmospheric
CO2
were included in the bean simulations but not in the maize simulations.
The deforestation scenarios (DEF) assume increased air temperature,
increased
incoming solar radiation and decreased rainfall, as predicted by
coupled
atmosphere-biosphere models for extensive deforestation of the Amazon
basin.
The CERES-Maize and BEANGRO crop simulation models, from the Decision
Support
System for Agrotechnology Transfer (DSSAT), were used for assessing
impacts
on yield of corn and black bean respectively. The results are only
relative
because the simulations assumed non-limiting nutrients and no damage
from
pests or from excess water. The assessments consisted of simulated
cultivations
of the CENIAP PB-8 maize cultivar grown during the wet season at three
sites for two baseline years (in order to cover different rainfall
conditions),
and the TACARIGUA black bean cultivar grown during the dry season at
three
sites, for only one baseline climate year. All GH scenarios caused a
decrease
in yield of corn at all sites: the phenological phases were shortened
and
the number and weight of kernels were reduced. Low sensitivity GH
scenarios
produced a slight increase in bean yield, but medium and high GH
scenarios
decreased bean yield, in spite of the partial compensation by
atmospheric
CO2 enrichment. Increases of precipitation in GH scenarios had no
effects
on maize yield, because the sites already have adequate precipitation;
however, the crop models used here do not account for potential
negative
effects of excess water. DEF scenarios produced relatively smaller
changes
in maize and bean yield. Increased solar radiation increased maize
yields
for the relatively small increase of air temperatures used in the DEF
scenarios.
Decrease of bean harvest index for all scenarios indicates that yield
is
more sensitive to air temperature change than is biomass. The potential
reductions in maize and bean yield will most likely be due to
increasing
temperatures and not to rainfall changes.
Key words: climate change, greenhouse effect, maize, beans, yield,
Venezuela,
deforestation.
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