Climate variability as experienced by farmers. [K-2224-04]
The typical approach of estimating crop response to future climate scenarios may be inappropriate in the case of smallholder multi cropping rain-fed agriculture. Indeed, a crop-by-crop simulation, based on current varieties, cannot take into account the dynamics among crops as well as within crops i.e. among varieties, in time and space. We implemented a comparative study to understand interactions between cropping system dynamics and pas climate variations, taking into account the diversity of farmers' experiences and socio-cultural organization. in Kenya, farmers who adopted maize a few years ago are still cultivating traditional sorghum and pearl millet varieties, while others abandoned them earlier in favour of maize. Farming systems were thus dynamic, with different crop assemblages over time. Thus, retrospectively, farmers' capacity to mitigate crop failure risk due to extreme rainfall events has never been constant. Has the farming system lost part of its capacity to cope with climate variability, as maize is known to be less resistant to drought than sorghum and pearl millet? While this is usually demonstrated using yield parameter, we used see losses, which is consistent with a multicrop system. Combining ecological anthropology and climatology, we confronted the results of a retrospective survey of farmers' seed loss reminiscence about the period 1961-2006 and climatic records for three altitudinal levels on the eastern slope of Mount Kenya were analysed. Over the period 3204 seed loss events were reported independently by 208 farmers, for eight main crops of their rain-fed farming systems. the causes given for these losses according to farmers' experience and knowledge were recorded yearly. We first assessed whether these causes were related to recorded rainfall values, and, second, analysed the proportion of lost seed on a yearly basis, crop by crop and on the whole farming system, using logistic regression. Drought was mentioned 73.5% of the time whereas 8.5% of the losses were attributed to heavy rainfall. Farmers recalls coincided on drought years associated with crop diversity losses: conditional Chi-square tests based on Monte Carlo simulation clearly rejected independence (p = 0.001) between climatic reasons given by farmers and recorded rainfall, for both droughts and heavy rainfall. Farmers' retrospective perception of drought corresponds to major droughts reported for Kenya. By favouring maize at the expense of sorghum and pearl millet, cropping system dynamics have promoted an increasing risk of drought-associated seed loss. t he probability to lose sorghum seed (0.056– 0.065) was significantly lower than the probability to lose maize seed (0.071–0.087). all crops were affected more by droughts than by heavy rainfall. s eed loss probability increased for a rainy season shorter than 50 days, with less than 28 rain days, and with a precipitation under 400 mm. l ogistic regression confirmed that a change in cropping systems increased the risk of seed losses due to drought over the 46-yr period. Farmers experienced climate variability differently, with greater negative impact on farmers cultivating maize. e cological and social components thus cannot be analytically isolated but have to be considered as parts of a socio-ecological system. While usual approaches consider present-day characteristics of agricultural systems to assess their adaptability to hypothetical rainfall variability (projection into the future), our study used farmer experiences to look into the past. i n our approach, past rainfall variability is already known, not hypothetical, while farmers' experiences can allow assessment of the evolution of their agricultural systems, which can be monitored over time, and related to climate variability. t he cropping system dynamics, by favouring maize at the expense of sorghum and pearl millet are partly related to agricultural policies that positively valued maize, whereas sorghum and pearl millet were devalued, being perceived as ''poor people crops''. The current dynamics of agricultural systems thus imply many dimensions, not only economical, political, and agronomical, but also cultural. (Texte intégral)
