Restoring riparian areas in oil palm plantations, and an introduction to the RERTA Project 

A blog post by BEFTA Programme and Insect Ecology Group postdoc Sarah Luke. Also posted at https://www.zoo.cam.ac.uk/research-groups/insect-ecology/news

Riparian zones are areas of land next to water bodies, including the banks of rivers, and streams, and the sides of lakes and ponds. They are a highly important habitat as they act as an interface between land and water. This means that they can often support a wide range of both land and water-associated species, as well as providing essential regulation of conditions within water bodies including inputs of leaves, woody material, sediment, nutrients, water flow, and control of water temperature through shading.

In agricultural areas, riparian zones are often protected in order to help protect water bodies from the impacts of agriculture. Strips of natural, or non-cultivated vegetation around waterways known as riparian buffers (or reserves, or margins) can help to trap soil and flood water that is washed off bare fields, prevent chemicals reaching waterways, and maintain natural conditions within the water body. They can also provide valuable natural habitat for both riparian and terrestrial species, areas of carbon storage, and contributions towards services such as pest control and maintenance of a clean water supply. Given their numerous benefits, multiple crop certification criteria, as well as government regulations, require that riparian buffers should be preserved in agricultural areas.

Forested riparian buffers within an oil palm landscape. Photo credit: Ed Turner

The BEFTA Programme’s research is based in oil palm plantations in Sumatra, Indonesia. Although natural forest buffers have been retained in some oil palm plantations, they vary in terms of habitat quality, and are completely absent in some areas. There is therefore a widespread need for restoration of riparian buffers. However, little research has been done into how best to do this in oil palm plantations. Along with collaborators from the Sinar Mas Agro Resources and Technology Research Institute (SMARTRI) in Sumatra, Indonesia, researchers from the BEFTA Programme are establishing a large scale, long term experimental project to test different strategies for riparian restoration in oil palm plantations: the Riparian Ecosystem Restoration in Tropical Agriculture (RERTA) Project.

The RERTA Project is making use of planned replanting within Sinarmas estates in Riau Province, Sumatra, to establish four different replicated riparian restoration treatments:

  1. Replanting oil palm right up to the river’s edge and leaving no riparian buffer (control treatment)
  2. Removing all oil palm and planting native tree seedlings within a 50m wide riparian buffer
  3. Leaving mature oil palms in place and allowing natural regrowth within a 50m wide riparian buffer
  4. Leaving mature oil palm as well as planting native tree seedlings within a 50m wide riparian buffer

The RERTA Project set-up before and after the experiment begins in early 2018

We will be assessing the impacts of these different treatments on a wide range of environmental variables, biodiversity of key taxa, ecosystem processes, and economic factors. We will be taking measurements before and after establishment of riparian experimental treatments using a before-after-control-impact (BACI) design. The RERTA Project began in September 2017. We are currently taking baseline, “pre-treatment”, measurements at our first RERTA site before experimental treatments are set up in February/March 2018. We then plan to take follow-up, “post-treatment” measurements soon after treatment set-up (June-July 2018), over a year after treatment set-up (late 2018), and in the longer term (pending additional funding).

Watch this space for updates as the RERTA Project unfolds!

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