Impact of herbivory on a semi-arid ecosystem: a compararative assessment of Lewa wildlife coservancy and Ol Pejeta ranch, Kenya
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Date
2012-02-10
Authors
Simiyu, Titus Wafula
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Abstract
The and and semi arid lands (ASALs) are fragile zones with high risk of degradation if improperly used. The zones have low and erratic forage supply yet this forage is expected to meet a relatively constant demand from grazing animals. The study assessed the herbivory pressure on two such habitats (01 Pejeta Ranch and LWC), determined the suitable mix of livestock/wildlife in the two habitats and assessed the severity of the 1999/2000 drought on the two wildlife/livestock production units.
Secondary data was obtained from existing records, while primary data was acquired through field observations, interviews and focus group discussions. Observation guides and interview schedules were the tools for data collection. Purposive sampling and stratified random sampling were used to get the respondents.
The Range Utilization Model (RUM) was used to estimate the herbivory pressure in the two habitats, while Prying Livestock Productivity Model (PRY) was used to determine the productivity of selected wildlife and livestock species in the habitats and hence the suitable species mix. Using a scale, respondents were asked to rate the severity of years 1999 and 2000 drought on vegetation resource. Numbers of animals that were lost due to the drought were also estimated. Data on vegetation degradation and animal losses together with rain all trends over the last three decades on 01 Pejeta Ranch and LWC were analysed to give an indication of the severity of the drought.
The results of RUM showed that annual dry matter production per hectare on 01 Pejeta Ranch was 0.588 tonnes, while annual demand per hectare was 0.874 tonnes. LWC had annual dry- matter production per hectare of 0.444 tonnes and annual demand per hectare of 0.754 tonnes. Therefore, LWC had a higher herbivory pressure than Ol Pejeta Ranch. However, both habitats were overstocked which caused a decline in the range conditions.
The results of modelling with PRY indicated that the buffalo (Syncerus caffer) with FEE of 21.10 Ksh/KgDM and eland (Taurotragus oryx) with FEE of 16.05 Ksh/KgDM were the most productive species on LWC and Ol Pejeta Ranch respectively. The impala (Aepyceros melampus) was the least productive species in the two habitats, with productivity indices of 9.85 and 4.69 Ksh/KgDM on LWC and 01 Pejeta Ranch respectively. Cattle (Bos taurus) and sheep ((his aries) with productivity indices of 5.82 and 5.14 Ksh/KgDM respectively on Ol Pejeta Ranch were less productive when compared with most wildlife species in the two habitats. Wild herbivores on LWC were found to be more productive than same species on 01 Pejeta Ranch. The relatively high productivity of most wild herbivores in the two habitats was due to their high viewing (tourism) value, but the good performance of the zebra (Equus burchelli and Equus grevyi) was associated with its highly valued skin. The blanket cropping rate of 6% recommended by KWS for all ranches in Laikipia region was found unsustainable on 01 Pejeta Ranch. Likewise, the absence (0%) of cropping on LWC was unsustainable.
During the 1999/2000 drought, 01 Pejeta Ranch experienced monthly rainfall' drop of 33.2 mm, which is more than half of the 59.2 mm monthly rainfall received on the ranch.
LWC had monthly rainfall drop of 15.5 mm from the average monthly rainfall of 41.8 mm. The reduction in precipitation made the basic range resources to decline both in quantity and quality in the two habitats. From professionals to locals, there was agreement that vegetation cover deteriorated heavily. On average, 18% and 15% of wild herbivores were lost on LWC and 01 Pejeta Ranch respectively. Ol Pejeta Ranch lost more of the very large species as compared to LWC. In addition, grazers suffered heavier losses as compared to browsers and mixed feeders.
Results of the Range Utilization Model showed that LWC and Ol Pejeta Ranch were under threat of degradation, hence the need to reduce herbivore populations in the two habitats. For ecological balance, it was recommended that most species on LWC be cropped at the rates of 6% and those of 01 Pejeta Ranch at rates between 6% and 10%, while the impala be cropped at the rate of 5% in both habitats. Substitution of some wildlife/livestock species by others to reduce competition and promote complementarity as well as increase income to the ranchers was also recommended. Development of a more proactive drought coping strategy was recommended to deal with the increasingly frequent droughts.
Description
The QH 77.K4S5
Keywords
Ecosystem management--Kenya--Ol Pejeta Ranch//Ecosystem management--Kenya--Lewa wildlife conservancy //Applied ecology--Kenya--Ol Pejeta Ranch//Applied ecology--Kenya--Lewa wildlife conservancy