The species has been previously identified as Ctenodesma borneensis (Zieritz et al. 2020). However, molecular phylogenetic analysis revealed that Khairuloconcha is a divergent lineage sister to C. borneensis and can morphologically be discriminated from C. borneensis by its sharper posterior ridge with nodulous sculpturing (especially dorsally) and a faint zigzag or irregular sculpture on the posterior slope rather than uniform plications (Zieritz et al. 2021).

This species is currently known from only one location in the Sungai Kemadi in the Limbang River basin (Sarawak, Malaysia), where it occurs at very low densities. The stream where it was found is within dense secondary forest. As the species could not be located in surrounding river basins or any streams situated within agricultural land despite intensive survey efforts, it is assumed that K. lunbawangorum is restricted to forested stream habitats of the Limbang River basin. However, across this basin, deforestation and land-use conversion to oil palm, pulp and timber plantations are ongoing, including the immediate vicinity of the only currently known site of the species. 84% of the currently remaining forest cover in the Limbang basin has been allocated to oil palm, managed logging, and wood pulp production (Global Forest Watch 2021, Earthsight Investigations & Global Witness 2021). Therefore, it is predicted that over the next 21 years, this land-use conversion will present an immediate threat of extinction to K. lumbawangorum from habitat loss.

This species is assessed as Critically Endangered CR A3c; B2ab(i,ii,iii) based on the predicted future loss of 84% of suitable habitat, and a current restricted distribution with an AOO of 4 Km², a single location, and continuous decline of AOO, EOO and habitat quality.

This recently described species is at present only known from a single site in a small stream (Sungai Kemadi) near Kuala Medalam in the Limbang River basin, Sarawak (Malaysia), where it was sampled in 2018 (Zieritz et al. 2020, 2021). The species was not found in adjacent river basins in Brunei and Sarawak, including the Tutong, Belait, Baram and Temburong river basins, which were also extensively surveyed recently (Zieritz et al. 2020). There are no historical records of the species or morphologically similar species (i.e. Ctenodesma spp.) from this area. As such, the presumed geographic range is the Limbang River basin only.

This species is very rare. At the only site it is currently known from, only three specimens were found after surveying for four person-hours (Zieritz et al. 2020). Due to the lack of historical data, data on current population trends are not available. However, considerable population losses are likely to have occurred and are still occurring due to loss of habitat following deforestation and forest degradation for managed logging, oil palm and wood pulp production across much of the species’ distribution range. This habitat loss and degradation is likely to continue, hence populations are likely to continue their decline in the future.

The species appears to have disappeared from sites where forest has been logged and converted to agricultural land (mainly conversion to oil palm plantations). Based on land cover change (data sourced from ESA Climate Change Initiative (2021)), by 2015, the species had lost at least 11% of its presumed original/natural distribution. Of the currently remaining forested area (including primary and secondary forest; ESA Climate Change Initiative (2021)) in the Limbang River basin (i.e. the species' assumed current distribution range), 84% are either “Managed Forest concessions” or “Sarawak Licenses for Planted Forests” (Global Forest Watch 2021, Earthsight Investigations and Global Witness 2021). We therefore estimate that 84% of the current habitat of this species will be lost in the next 21 years (three generations) unless there are significant efforts to conserve the habitats of this species.

The species appears to be restricted to forested stream habitats. The species is only known from a cool, relatively pristine stream situated in a dense secondary forest with natural bank vegetation (Zieritz et al. 2020).

Estimates suggest that Borneo supports about half of the global planted area with oil palm and small-holder plantations (>7.9 Mha). Pulpwood plantations, including the fast-growing Acacia and Eucalyptus, are also a major contribution to the region’s economy (Gaveau et al. 2016). From 1973 to 2015, large tracts of old-growth lowland forests were degraded by selective timber cutting, illegal logging, droughts, and fires (Gaveau et al. 2016). The Limbang basin has been particularly affected by these activities and is now dominated by oil palm, wood pulp and selective logging concessions. Large areas of forest cover in the northern region of the basin have already been converted for these activities, while the total area of primary forest decreased by 12% across the whole basin in the past 20 years (estimation based on data from Hansen et al. 2013, Turubanova et al. 2018). This deforestation and land-use changes present a threat to K. lunbawangorum by rendering the habitat unsuitable directly to the mussels (e.g. via increased sedimentation and pollution) and indirectly by reducing fish populations that they require to complete their life cycles (Zieritz et al. 2020). This threat is expected to continue and intensify over the next 21 years, as companies hold large, forested areas as ‘land banks’, which will soon be converted to logging and oil palm monocultures due to ongoing demand and economic pressure (Hon and Shibata 2013). In fact, the only location that K. lunbawangorum is currently known from is situated in an unprotected area that has been allocated to an oil palm plantation (Zieritz et al. 2021). The surrounding area includes logging and wood pulp concessions, covering almost all the available habitat where the species could plausibly occur. Specifically, of the currently remaining “forested” area (including primary and secondary forest; ESA Climate Change Initiative 2021) in the Limbang basin, which is considered the current distribution area of the species, 84% are either “Managed Forest concessions” or “Sarawak Licenses for Planted Forests” (Global Forest Watch 2021, Earthsight Investigations & Global Witness 2021). We therefore estimate that 84% of the current habitat of K. lunbawangorum will be lost in the next 21 years. This threat is ongoing and presents an imminent risk of extinction to this newly discovered species. Other possible threats include pollution from domestic and industrial sewage, climate change, and invasive species introductions (Dudgeon et al. 2006, Zieritz et al. 2018). Latter include the Chinese Pond Mussel Sinanodonta pacifica (Heude, 1878), which may compete with K. lunbawangorum for resources and contribute to habitat degradation (Douda et al. 2024 and references therein), and the widespread introduction of non-native fish species, including tilapia and catfish (Rahim et al. 2013), which potentially displace native fish hosts of C. borneensis.

The species is occasionally harvested as a food source by the local indigenous tribe, with negligible impact on the species.

We recommend urgent survey work to identify yet unknown populations and characterize and monitor their distribution, population characteristics, ecology, and biology, as well as their habitat trends. This should include the collection of data on potential threats and population structure to base the design of targeted conservation measures. Given the surrounding area of the current population has already been assigned for oil palm production and is likely to be undergoing imminent and rapid land-use changes, mitigation strategies are also recommended. This could include the establishment of riparian buffer zones (which are required by law but are often not implemented), and outreach programmes to improve awareness of stakeholders, decision-makers and the public. Given the low population size, captive breeding programmes for reintroduction and augmentation are recommended. Measures to control invasive fish species that negatively affect fish hosts of K. lunbawangorum, may be needed. Local practitioners will need training to implement any conservation actions. Development of a Species Action/Recovery Plan and/or area-based management plan with relevant stakeholders is urgently recommended for this species.