Replanting reduces frog diversity in oil palm

July 05, 2016

A new article lead-authored by graduate student David Kurz and published in the journal Biotropica finds that management decisions within tropical agricultural landscapes have a profound impact on biodiversity. 

A mature, older oil palm plantation over 20 years old, with much more vegetative structure and canopy cover than a young oil palm plantation. Photo credit: David Kurz

It’s well established that oil palm expansion at the expense of rain forest hurts wildlife, but are the hundreds of square kilometers of oil palm in Southeast Asia a complete loss for conservation? Is there any way to improve oil palm for native animals and plants?

One of the key characteristics of oil palm and other plantation crops is that they undergo a lifecycle in which the trees mature for a number of years before being periodically cut and replanted with young trees. This cycle leads to dramatic changes in the vegetative structure, temperature, humidity, and canopy cover of plantations, presumably with major implications for the wildlife that live within them. However, until now no studies had quantified the degree to which the abrupt turnover in this life cycle influences flora and fauna, and how the process of re-planting can be improved for conservation purposes in plantation crops.

A new study just published in the July issue of the journal Biotropica provides the first insights into ways that intelligent management of the oil palm lifecycle can benefit frogs. The Indonesia-based study, published by researchers at the University of Cambridge, MIT-Woods Hole, the University of Würzburg, and the SMART Research Institute, found both a higher number of frog species and a greater number of total frogs in older oil palm plantations than in younger ones. In addition, the types of frogs found in the two types of oil palm changed, with older oil palm containing more frog species typically associated with forested environments.


Hylarana glandulosa, a frog native to Sundaland and abundant in young and older oil palm plantations. Photo credit: David Kurz

By tweaking the way in which oil palm re-planting is managed, the researchers conclude that frogs and potentially other types of wildlife could do much better in these agricultural landscapes. Instead of re-planting huge areas of oil palm all at once, the new research suggests that estate managers could re-plant in a staggered way that ensures older oil palm patches stay connected. In this way, frogs could move between the connected older oil palm areas, allowing a more diverse collection of frogs to persist in the landscape, even during the replanting process. 

These findings are encouraging, says lead author David Kurz, now a PhD student at the University of California, Berkeley. “We’ve known for a long time that we need to protect large areas of forest, but our study provides hope that important conservation efforts can also take place in ordinary working landscapes like oil palm.”

The study is part of a long-term project – the Biodiversity and Ecosystem Function in Tropical Landscapes project, a collaboration between University of Cambridge researchers and the Sinar Mas Agro Resources and Technology Research Institute – that seeks to improve the long-term sustainability of tropical landscapes through creative management efforts that support both economically and environmentally beneficial processes. Implementing management practices like this is particularly important given the large amount of oil palm currently being replanted, due to a boom in oil palm planting in the mid 1980s and the roughly 30 year life cycle of oil palm.

As oil palm continues to expand in Southeast Asia, more studies like this one will need to be carried out for the many different types of wildlife that live in oil palm – such as beetles, ants, dragonflies, small mammals, bees, bats, snakes, and birds. Kurz and his co-authors are confident that a number of management efforts, from novel re-planting approaches to maintaining understory structure in oil palm, can help. According to Kurz, “Every little step we can take to keep agricultural areas as full of biodiversity as possible is a win, particularly given that we can often support wildlife in inexpensive ways. Wildlife are inherently valuable, plus they often have positive impacts on the overall ecological function of the landscape.”