Asian elephants (Elephas maximus) have co-existed with human practices for thousands of years, including shifting cultivation. Shifting agriculture encompasses a variety of different practices that involve abandoning plots for periods of time to allow natural vegetation to grow. The practice consists of cutting and burning the natural vegetation at the end of the dry season and cultivating with the rains. Harvesting is completed by the end of the wet season. Traditionally, in Sri Lanka, fields are cultivated for two or three consecutive years and left fallow for four to five. Often, areas are not able to be cultivated due to lack of investment in ground preparation, creating an unusual mosaic of active fields, successional forests, and mature forests. But according to a new study in mongabay.com’s open-access journal Tropical Conservation Science, traditional shifting cultivation is also important elephant habitats in the dry seasons.
In recent decades, however, constraints of space, legal obstacles to clearing forest, and the desire to obtain greater harvests have lead to longer harvest periods and an increasing number of years before the land is abandoned—if it ever is. In addition, the use of fertilizer and irrigation, rather than natural regeneration of nutrients, is steadily replacing the traditional regime.
Asian elephants actually prefer successional diversity found in the forest edge over the homogeneous interior of the forest. Elephants are generalist feeders, consuming a large number of species found in the environment. However they do prefer grass, because it lacks toxic secondary compounds and contains a high amount of protein, and a few species constitute a major part of their diet.
In Sri Lanka, elephants have historically preferred shifting agriculture areas during the dry season, which runs from March until September. Many of the food species favored by elephants are pioneer species, which rely on rapid growth and mechanical rather than chemical defenses against herbivores. Pioneer species account for the majority of the vegetation in shifting agriculture areas.
Scientists collared two elephants to track their locations during the study. The first was a five to six year old juvenile representing a group of around fifteen females and young. The second was a solitary adult male. After about ten years, males typically lead a solitary life. Gathering data on the range of elephants largely indicates the type of vegetation consumed because elephants feed between twelve and eighteen hours every day.
During the wet season, protected areas such as the Yala National Park and Nimalawa Sanctuary housed the elephants. But, as the farmers vacated the fields after harvesting, the elephants moved into the fields. Both tracked elephants lived almost exclusively in shifting agriculture fields during the dry season. This allows for both the famers and elephants to use the same land with little conflict. The greater use of shifting agriculture lands during the dry season indicates that it is a vital resource for Asian elephants.
This study concludes that cultivating fields for longer time periods or not fallowing at all will likely decrease the benefit for elephants. These two changes cause decreased regeneration of natural vegetation and over the long term, more intensive cultivation is likely to result in fields becoming barren and non-productive. Extending the cultivation period into the dry season with irrigation would also disrupt the existing temporal resource partitioning between farmers and elephants and lead to more conflicts between them. Managing shifting cultivation in Sri Lanka with a prescribed shifting regime and annual cultivation period would benefit both agriculture and elephant conservation, according to the scientists.
Asian elephants in Bukit Barisan Selatan National Park. Photo by Rhett Butler.
Citations:
- Pastorini, J., Janaka, H. K., Nishantha, H. G., Prasad, T., Leimgruber, P., and Fernando, P. 2013. A preliminary study on the impacts of changing shifting cultivation practices on dry season forage for Asian elephants in Sri Lanka. Tropical Conservation Science Vol. 6(6): 770-780.
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