Abstract
Remote sensing techniques have been widely used to monitor moisture-related vegetation conditions. Vegetation vigour response to drought however is complex and has not been adequately studied using satellite sensor data. This paper investigated the time lag response of vegetation to drought in Kenya’s Chyulu-Amboseli ecosystem based on Standardized Precipitation Index (SPI) derived from monthly precipitation data for the period January 2000-October 2016 downloaded from the Climate Hazards group InfraRed Precipitation with Stations and Normalized Difference Vegetation Index (NDVI) computed from Moderate Resolution Imaging Spectro-radiometer (MODIS) pre-processed images downloaded from the University of Natural Resources and Life Sciences (BOKU) database. Statistical analysis showed that drought severity increased over the study period while corresponding vegetation conditions degenerated. Results further revealed that the relationship between drought and vegetation greenness was significant (R2 = 0.6) with 2 months optimal lag. This calls for policy makers and programme managers to integrate the lag effect in measures to cope with drought in the rangelands.Keywords: Drought, Vegetation greenness, Chyulu-Amboseli, Statistical Analysis, Rangeland
Highlights
Drought is one of the biggest threats to Kenya’s socioeconomic and environmental development in arid and semi-arid lands (ASALs) (RoK, 2015)
Descriptive Statistics: Results of the Standardized Precipitation Index had a mean of -0.26, median -0.35, maximum 3.26, minimum -4.64, and a standard deviation of 1.32
The year 2009 had the most prolonged period when Normalized Difference Vegetation Index (NDVI) values were below the mean, thereafter, there were quick succession of droughts events resulting in some years like 2012 recording rapid changes in vegetation conditions
Summary
Drought is one of the biggest threats to Kenya’s socioeconomic and environmental development in arid and semi-arid lands (ASALs) (RoK, 2015). Defined as the extreme persistence deficiency in precipitation over an extended period usually a season or more (Tale and Gustard, 2000) drought results in a water shortage causing adverse impacts on ecosystems, livelihoods or societies (Kassahun et al, 2008; Opiyo, et al, 2015; Tuqa et al, 2014). Drought is a normal characteristic of these areas, rise in frequency and severity has adversely affected livestock production, both directly and indirectly (RoK, 2012; Ngaina et al, 2014). Whilst direct effects result from associated high temperature which influence animal growth, milk production, and reproduction; indirectly drought affects the quantity and quality of feedstuffs such as pasture, forage, and the severity and distribution of livestock diseases and parasites (Houghton et al, 2001; Seo and Mendelsohn, 2007). Such knowledge is important in informing the design of drought risk reduction strategies in rangelands
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