Forest Conversion to Oil Palm Compresses Food Chain Length in Tropical Streams

Wilkinson, Clare L.; Chua, Kenny W. J.; Fiala, Roswitha; Liew, Jia Huan; Kemp, Victoria; Fikri, Arman Hadi; Ewers, Robert M.; Kratina, Pavel; Yeo, Darren C. J.

doi:10.1002/bes2.1826

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“…The persistence of some native shrimps in degraded habitats therefore probably reflects their tolerance of various land‐use changes (Pérez‐Reyes, Crowl & Covich, 2016) and an ability to exploit resources within modified habitats (Chong & Khoo, 1987; Cai et al, 2016; Khoo et al, 2019). This ability may be explained by the generalist/adaptive feeding behaviour of some Macrobrachium species (March & Pringle, 2003; Snyder, Small & Pringle, 2015), allowing them to maintain their diets in similar fashion to meso‐predators such as fish (Wilkinson et al, 2021). Another possible explanation is that certain Macrobrachium species are able to exploit disturbance‐resilient macroinvertebrates (e.g.…”

Section: Discussionmentioning

confidence: 99%

Forest conversion adversely affects native Macrobrachium shrimp assemblages in tropical Malaysian streams

Gan

Tan

Ahmad

et al. 2022

Aquatic Conservation

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1. Commodity-driven forest conversion represents one of the most severe threats to freshwater biodiversity in Southeast Asia, notably causing population declines and the extinction of freshwater fish species.2. Although a variety of freshwater taxa are likely to be adversely affected by forest conversion, little is known about the impact on ecologically and economically important invertebrates such as decapod crustaceans.3. This study evaluated the impact of forest conversion and land-use change on freshwater Macrobrachium shrimp species, using species richness, abundance, and environmental data collected from 20 streams across southern Peninsular Malaysia.Streams were located in three types of landscape: forest; oil palm plantation; and mixed land use, comprising young secondary forest, small-scale plantations, patches of open and sparsely vegetated areas, and agricultural fields and clearings.4. Generalized linear models showed that even incomplete change from forest habitats to mixed land use and oil palm plantation resulted in significantly lower Macrobrachium native species richness and higher non-native species abundance.Native species richness was positively correlated with canopy cover, leaf litter, substrate size, and dissolved oxygen, and was negatively correlated with water temperature and conductivity. Native species richness was also negatively correlated with non-native species abundance, with non-native species abundance increasing along the human disturbance gradient.5. These results highlight the need for riparian habitat protection to conserve native Macrobrachium and limit the spread of non-native species. A management priority should be to maintain or restore optimum instream habitat conditions for shrimps, which would also benefit fish and other benthic macroinvertebrates. Suitable riparian management requires substantial support and funding from multiple stakeholders, but it can be aligned with other catchment-based strategies to optimize the use of limited resources available for freshwater biodiversity conservation.

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Section: Discussionmentioning

confidence: 99%

Forest conversion adversely affects native Macrobrachium shrimp assemblages in tropical Malaysian streams

Gan

Tan

Ahmad

et al. 2022

Aquatic Conservation

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“…Terrestrial and aquatic vegetation form key ecosystem structures that provide resources, shelter and physical conditions that benefit a variety of species and functional groups (Teixeira de Mello et al, 2015; Tews et al, 2004; Wilkinson et al, 2021). Density and morphology of plants often underly habitat heterogeneity (Diehl & Kornijow, 1998; Tews et al, 2004; Warfe & Barmuta, 2004), which is essential for resilient, abundant and diverse animal communities (Kovalenko et al, 2012; Teixeira de Mello et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Direct and indirect influences of macrophyte cover on abundance and growth of juvenile Atlantic salmon

et al. 2022

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The relationships between macrophytes and the physical and biological characteristics of the environments that aquatic organisms inhabit are complex. Previous studies have shown that the macrophytes, Ranunculus (subgenus Batrachium), which are dominant in lowland chalk streams and widespread across Europe, can enhance juvenile Atlantic salmon abundance and growth to a greater degree than other physical and biological habitat characteristics. However, mechanistic understanding of how this effect might arise requires consideration of the direct and indirect relationships among habitat characteristics that are likely to be influenced by the presence of macrophyte cover. We applied structural equation modelling to data collected during a 2‐year in‐river manipulative experiment in the River Frome (southern England, U.K.) designed to quantify the magnitude and the relative importance of direct and indirect influences of Ranunculus cover and other physical and biological variables, including water velocity, water depth, prey biomass and body size, and abundance of con‐ and hetero‐specifics, on abundance and somatic growth of 0+ salmon. Results indicated a strongly positive direct influence of Ranunculus cover on salmon abundance, as well as positive influences of Ranunculus on velocity heterogeneity and water depth that are indirectly related to decreased salmon abundance. Interestingly, there was no indication of a direct influence of Ranunculus cover on salmon growth, although Ranunculus was indirectly related to increased salmon growth through its positive influence on prey biomass, an effect mediated by velocity heterogeneity and proportion of fast velocities. These findings provide novel mechanistic insights into the key role of Ranunculus in their native lowland rivers to enhance abundance and improve conditions for multiple food web components. Strategies to maintain or enhance naturally occurring Ranunculus in these rivers are therefore likely to return wide ranging ecosystem benefits, including for species of high conservation value, such as salmon. These mechanistic impacts on habitat heterogeneity and ecosystem productivity could generalise to native macrophytes in other river systems, particularly where habitat is dominated by vegetation in the absence of large substrates.

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Forest Conversion to Oil Palm Compresses Food Chain Length in Tropical Streams

Cited by 2 publications

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Forest conversion adversely affects native Macrobrachium shrimp assemblages in tropical Malaysian streams

Forest conversion adversely affects native Macrobrachium shrimp assemblages in tropical Malaysian streams

Direct and indirect influences of macrophyte cover on abundance and growth of juvenile Atlantic salmon

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