- Demand for agricultural land threatens Peninsular Malaysia’s remnant native forest cover, and with it, Malaysia’s rich bird life.
- A recent study has found that agroforestry and polyculture plantations — those with a greater number of tree species — provide a more complex habitat for bird life and are better structured to support biodiversity.
- The study suggests that the introduction of fruit trees that encourage bird life into monoculture croplands would benefit farmers through the restoration of ecological functions, such as reducing the need for pest control through bird diet without compromising yield.
Malaysia is the second-largest palm oil producer in the world, behind only Indonesia. In 2020 alone, Malaysia was responsible for more than a quarter of global palm oil production. But for the country’s forests and wildlife, plantation agriculture is an industry that comes at a cost.
Across Peninsular Malaysia, where nearly half of the country’s palm oil is produced, demand for agricultural land is increasing in step with population growth and expanding commercial use of oil palm. And while 84% of Peninsular Malaysia’s remnant native forest cover is classified as permanent forest reserve, these forests remain threatened by land clearing, and with them the rich bird life that depends on the habitat these forests provide.
A recent study presents one possible way to mitigate the threat habitat loss poses to Malaysia’s bird life: the creation of more diverse agroforestry systems. These multicrop agricultural environments create a more complex habitat for birds — and might just benefit farmers too.
The study, published in Forest Ecology and Management, compared and analyzed the number and type of bird species found in plantations of oil palm (Elaeis guineensis) and rubber tree (Hevea brasiliensis) in Peninsular Malaysia against agroforestry orchards, where multiple species are grown in the same plantation. In doing so, it sought to determine the overall effect of changes to land use on bird biodiversity in the region.
The researchers found more species in mixed orchards than in monoculture plantations, suggesting that agricultural areas with more tree species are better structured to support bird diversity. The results also suggest that introducing fruit trees to encourage bird life into monoculture croplands would benefit farmers through the restoration of ecological functions, such as reducing the need for pest control through bird diet, without compromising yield.
Diverse trees support diverse birds
The research was conducted in Rembau, situated in the state of Negeri Sembilan on Malaysia’s west coast. Rembau’s economy is driven by agriculture, with predominant production of oil palm, rubber and tropical fruits such as durian (Durio spp.), rambutan (Nephelium spp.), mangosteen (Garcinia mangostana), jackfruit (Artocarpus heterophyllus) and petai (Parkia speciosa).
In 2018, the research team counted the total number of birds sighted at 180 separate locations across agroforestry, oil palm and rubber plantations. They recorded a total of 110 species from 6,248 bird encounters.
Agroforestry orchards had the most birds (2,653 spotted) and the most species (92). By contrast rubber tree plantations had 88 species from 1,792 bird sightings, and oil palm plantations 66 species from 1,803 sightings.
Overall bird abundance in agroforestry orchards was an average of 22.29 birds per bird count site, compared with 15.27 in rubber and 14.97 in oil palm sites.
The study’s results indicate that the different agricultural land use types play a significant role in bird biodiversity, study co-author Badrul Azhar of Putra Malaysia University’s Department of Forestry Science and Biodiversity, told Mongabay.
“Our results revealed that bird species richness and relative abundance were significantly greater in agroforestry orchards than the other two agricultural habitats,” Azhar said. “Bird abundance was similar in oil palm and rubber tree plantations, but rubber tree plantations supported significantly more species.
“Our results also demonstrate the ability of agroforestry orchards to support more bird dietary groups, such as frugivores, insectivores, omnivores and granivores,” he added.
A high abundance of insectivores, such as the common tailorbird (Orthotomus sutorius), Germain’s swiftlet (Aerodramus germani) and common iora (Aegithina tiphia), was identified in the study as potentially beneficial to agricultural landowners through biological pest control through their primary diet. Insectivores can help keep insect numbers down, reducing the need for chemical pesticides.
The glass ceiling of monoculture resources
Azhar’s team concluded that multiple tree species, or polyculture farming, increases diversity through additional food, prey and shelter resources for birds. An agroforestry orchard, for example, has a multistory tree canopy height with two or more permanent fruit trees that enable crucial habitat for birds, while plantations are characterized by a single commodity crop species of similar height and age. In addition, the more diverse ecosystem has the capacity to create habitat connectivity, or a “wildlife corridor,” which promotes movement of species between neighboring forests and plantations.
Moreover, the study identified a high number of invasive bird species in monoculture plantations compared with native bird species. Although there were also invasive species recorded in agroforestry orchards, this environment is able to support the needs of native and invasive species alike.
Through this, the authors conclude that monoculture crops provide fewer resources for bird species compared with native forest, or more diverse agroforestry orchards. This simplified environment increases competition between species due to limited food and roosting sites. Invasive species can often be better adapted to exploiting these resources in more open, human-altered landscapes such as plantations.
“In our case, the Javan myna [Acridotheres javanicus], which is an invasive species, tends to be very good at exploiting those available resources and establishing their populations compared to the other co-occurring species, such as the common myna [Acridotheres tristis] and jungle myna [Acridotheres fuscus],” Azhar said.
“However, further investigations are needed to understand the link between the role of industrial-scale monoculture cultivation and the expansion of invasive species populations,” he added.
Sustainability in agricultural landscapes: A global challenge
The development of sustainable practices in highly intensified agricultural landscapes is a global challenge. This, the authors say, is compounded by a historical undervaluing of the conservation potential of farmland biodiversity.
Biodiversity-friendly farming practices, which are usually less intensive, are often perceived to be unrealistic and impractical, and to result in smaller yields. This, in turn, has meant their conservation potential is either neglected or not fully recognized by stakeholders in the sector.
“Our work can provide useful insights to plantation managers, smallholders, and policymakers regarding the importance of habitat heterogeneity to improve biodiversity within industrial large-scale monoculture plantations,” Azhar said. “We hope those key stakeholders would adopt the ideas presented in the paper as part of their efforts to make large-scale agricultural landscapes, particularly oil palm, more sustainable and biodiversity-friendly.
“To reconcile intensive farming with biodiversity conservation, small-scale farmers and plantation businesses should be encouraged to plant native fruit trees within or nearby monoculture plantations,” he added.
Daniel Karp, an assistant professor at the University of California, Davis, who was not affiliated with the research, said the study shows that agriculture can play a role in conservation of avian biodiversity. “There is good potential for diversified farming systems — like the orchards mentioned in this study — to serve as corridors of movement between more ‘natural’ areas,” he said.
Despite this, Karp stressed the importance of continued efforts to protect remnant native vegetation.
“While diversified farming and agroforestry can yield clear benefits for biodiversity, as well as the benefits it provides to people, protecting larger swaths of natural vegetation is also essential to conserve many species,” he said.
“This paper supports the idea that a conservation ‘toolkit’ should include both establishing protected areas and explicit incentives for farmers to diversify production,” he said. “These complementary strategies are probably what is needed to holistically address the ongoing biodiversity crisis.”
Banner image: Black-and-yellow broadbill (Eurylaimus ochromalus), a near threatened bird species recorded during point count surveys in an agroforestry orchard in Rembau, Malaysia. Image courtesy of Muhammad Syafiq Yahya.
Yahya, M. S., Atikah, S. N., Mukri, I., Sanusi, R., Norhisham, A. R., & Azhar, B. (2022). Agroforestry orchards support greater avian biodiversity than monoculture oil palm and rubber tree plantations, 513(1). doi: 10.1016/j.forenco.2022.120177.
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