Climate change in the subtropics:

The impacts of projected averages and variability on banana

productivity J. Ramirez, D. Turner, I. Van den Bergh, C.

Staver, D. Brown and A. Jarvis

ESRI User Conference – July, 2011

Introduction Bananas are of tropical origin when grown in

subtropics, they are subject to strong environmental constraints, mainly low temperature but also drought

Temperature and rainfall are expected to change at unprecedented rate in coming decades (IPCC, 2007) potentially huge impact on banana production, both in tropical and subtropical regions

Review of the impacts of climate change on Musa (Ramirez et al. 2010) suggests that future climates will be less suitable in >70% of global land areas (mainly tropical areas), but there could be gains towards subtropics

Introduction But more profound analysis is required:

Subtropical production of bananas is highly diverse activity

Varieties used in the subtropics are likely to be adapted to different conditions of annual variability in climates than tropical varieties

Some impacts and responses are largely site specific and thus so are the adaptation measures

A calibrated approach only for subtropical production of bananas is required

Our objective was to estimate the effect of expected climate changes on banana production in the subtropics

Methodology Five-stage analysis:

1. Identification of current banana areas by means of expert consultation

2. Calibration of a model and modeling of the suitability of current banana production areas

3. Modeling of expected suitability (i.e. 2020s, 2050s) and changes in suitability of subtropical banana production areas

4. Analysis of changes in yearly seasonality

5. Identification of homoclimes for potential technology transfer options

Identification of current banana areas by means of expert consultation

Steps:

Send the country map to a expert on that country

Expert marks over the map banana production areas

Expert send back the map to us and we digitize the map

Identification of current banana areas by means of expert consultation

Methodology Current climate data derived from WorldClim

(Hijmans et al. 2005, http://www.worldclim.org) Climate surfaces for monthly maximum, minimum,

mean temperatures and total monthly precipitation used to characterize the locations where banana production was identified by experts and to model the suitability of these locations for bananas

Future projections of global climate data obtained at original Global Climate Model resolution from the Coupled Model Inter-comparison Project, phase 3 web data portal, under Earth System Grid online platform (https://esg.llnl.gov:8443/index.jsp)

Methodology EcoCrop model: uses mean and min/max monthly temperature and

monthly precipitation data to evaluate the suitability of a location for a crop

Model calibration for subtropical banana: Growing season duration Gs = 365 days Monthly min temperature below which crop dies Tkill = 0°C Monthly min temperature below which crop stops growing Tmin = 12°C Monthly max temperature above which crop stops growing Tmax = 33°C Optimum growth between Topmin = 17.5°C and Topmax = 26.3°C Rainfed crop fails due to drought below Rmin = 200 mm/year Crop fails due to waterlogging above Rmax = 4,000 mm/year Optimum growth between 900 and 1,760 mm/year and good drainage

Definition of suitability ranges: Beyond absolute thresholds (Tmin, Tmax, Rmin, Rmax): suitability 0% Between absolute and optimum thresholds: suitability 1-99% (linear) Within optimum conditions: suitability 100%

Calculations for precipitation and temperature done separately; their product is final suitability score

Results: Current suitability + limiting factor

Results: 2020s suitability + change

Results: 2050s suitability + change

Results: Homoclims Northern India

Southern Brazil

Discussion and conclusions Current banana production in subtropics

challenged mainly by low temperature and drought

In future, temperature expected to increase in all subtropical areas investigated, while changes in rainfall patterns vary

Discussion and conclusions Adaptive strategies for subtropical banana production will

need to focus on drought adaptation, while maintaining

attention for below-optimal temperature:

Change in crop management and technology transfer to

vulnerable areas: Improved irrigation technology, targeted

planting dates and water application to reduce water demands

and exposure to low temperatures and for key market periods,

soil/water management to increase water capture and holding

capacity

Change in cultivars: Substitution of cultivars with greater

tolerance to drought and temperature extremes

Discussion and conclusions…

Genetic improvement: Centre of origin of Musa is SE Asia where

climatic conditions are highly variable, but domestication

occurred in humid and/or sub-humid climates Musa genepool

has only been barely exploited for traits related to abiotic stress.

Some wild species are known to hold useful traits, including

tolerance to cold (M. sikkimensis, M. basjoo, M. thomsonii) and

drought (M. balbisiana, M. nagensium)

Expansion of area: Based on increasing minimum temperatures,

and in those areas where rainfall or maximum temperatures are

not (or do not become) limiting

Thank you