Assessing The Suitability Of Tea Growing Zones Of Kenya Under Changing Climate And Modeling Less Regret Agrometeorological Options.

Abstract

The suitability of tea production within the tea producing counties in Kenya by the years 2050 and 2070 was determined by the use of various methodologies where both ground based and satellite data was used. Tea production data from Tea Directorate of Kenya (TDK) and monthly precipitation, minimum and maximum temperature data for the period 1976-2014 from Kenya Meteorological Department (KMD) was used and supplemented with gridded data from Atlas KNMI.Data was analyzed to establish the trends, magnitude and frequency of extremes and the relationship between tea, temperatures and precipitation using R software. Bioclimatic variables data from National Centre for Meteorological Research (CNRM) model with worldclim.com using 1 resolution was extracted into the area of study and converted into a format readable in MaxEnt model using QGIS model. The QGIS model outputs were fed into the MaxEnt model as environmental layers together with samples data with different bioclimatic species under investigation through which the suitability of tea growing areas for tea and coffee production by the years 2050 and 2070 was determined. Suitability of the tea growing zones for climatic constraints such as frost and thunderstorms, existing pests such as tea Kangaita weevil, tea mosquito bug and existing crop diseases such as tea disease, was also determined. Analysis of climate variability indicated that both the magnitude and frequency of precipitation and temperature variability have increased. Multiple linear regression between precipitation, maximum and minimum temperature indicated that night temperatures had a greater effect on precipitation compared to daytime temperatures. It was deduced that rainfall and temperatures in the highlands east of rift valley and Kericho correlated positively. vii On the other side, it was found out that rainfall and minimum temperatures in the highlands west of rift valley correlated positively while correlated negatively with maximum temperatures. Multiple linear regression between tea, maximum and minimum temperatures and precipitation showed that temperatures and especially night temperatures had more effect on tea production as compared to precipitation. Maximum and minimum temperatures and precipitation were found to positively correlate with tea yields in the highlands east of rift valley. Conversely, maximum and minimum temperatures negatively correlated with tea yields, while precipitation positively correlated with tea yields in the highlands west of the rift valley. Peak seasons for tea production were found out to be MAM and OND with December experiencing the largest amounts of yields. Tea yields have been increasing until 2014 after which yields dwindled and the above normal production episodes were found out to be more as compared to below normal episodes. The suitability analysis indicated that, around a half of the tea growing area in Kenya is going to be unsuitable for tea production by the year 2050 while only 40% of the region will be unsuitable by the year 2070. White tea is expected to be the most resilient variety to the changing climate for the highlands east while black tea the most resilient variety for the highlands west by the year 2070.Counties which might not be able to produce any tea variety in most parts such as Nyandarua, Nyeri north, parts of Kiambu and Nakuru are expected to be able to produce coffee as an option since coffee can bear more severe temperatures. Tea suitability drop was found out to be as a result of the hot season JFM getting warmer and the tea peak seasons which are also the wet seasons MAM and OND getting cooler. The cost of production for tea is likely to increase as pests broaden their coverage and tea disease prevalence intensify, especially over Transzoia, Nandi and most parts of the highlands east. This will as well affect the quality of Kenyan tea which is usually less sprayed with chemicals.