Page 87 - Ecuador's Banana Sector under Climate Change

chapter 4: assessment of climate change impact on banana production and suitability in ecuador, and general assessment of global banana trends under climate change scenarios
unchanged - with a small annual increase of 200 mm in total. The average temperature will increase over the next 50 years by over 3°C from 25°C to 28°C. This is a general effect across all six sites. Even with these changes, the average growing conditions for banana will remain favourable in the major banana growing areas of Ecuador. An average temperature of 28°C is still within the optimum range, while irrigation and drainage will continue to be an important element of crop management.
The analysis, based on growing conditions for banana, provides an overview of the effects of average climate change. Diverse tools have been used to convert the general requirements for growth into more quantified effects. For example, Climate Envelope Models, such as Maxent, Bioclim and Ecocrop, have been applied for many different crops and natural ecosystems, and Ecocrop
has been used in relation to the banana (Van den Bergh et al., 2012). Models, such as Ecocrop, use annual data for temperature and rainfall, which limit their applicability for crops, which have a 12- month cycle and which may use irrigation.
To have a quantitative index of the effects of changing temperature and
water availability on banana growth, a calculation was developed, using monthly temperature and rainfall based on leaf emission rate. Leaf emission rate is a key variable in banana productivity, since the rate of leaf emission is closely correlated to the length of the vegetative cycle and the duration from one bunch to the next for each banana mat. Leaf emission rate is highly influenced by temperature
and available water. Three calculations were carried out: (i) effect of temperature alone, measured by growing degree days (GDD); (ii) thermal development units (TDU) in which GDD are combined with available soil water; and (iii) water deficit based on a water balance, using natural rainfall and optimum crop needs. All three calculations were carried out for current conditions and compared with projections for 2030, 2050 and 2070.
2.2.1. Estimation of banana GDD and TDU
GDD were used as a measure of temperature requirements for banana plants and could be used to estimate growth and development. Banana plants are generally considered day-neutral plants because floral induction is not highly dependent on photoperiod. (Some effect has been shown by Fortescue et al., (2011), but the effect has been left out for this analysis.) The anthesis or flower emergence thus occurs at any time of the year, and the emergence of the bunch may be influenced seasonally by only environmental and edaphic factors. As the photoperiod does not influence bunch initiation, the development of the plant can be best described by growing-degree-days (GDD, with units of oC days).
The basic concept of GDD is that plant development will occur when temperatures exceed a base temperature and decrease when a maximum temperature is exceeded. For the estimation of GDD, the average temperature of the month was used. The base temperature is then subtracted from the monthly average temperature to give a daily GDD. If the daily GDD calculates to a negative number, it is made equal to zero. Monthly GDD was calculated multiplying the number of days of the month and then added up (accumulated) over the year:
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