Thames Door Snail (Balea biplicata)
Key Details
| Taxonomic Groups: | Invertebrate > mollusc > Mollusc (non-marine) |
| Red List Status: | Vulnerable (Not Relevant) [VU(nr)] |
| D5 Status: | Included in the baseline Red List Index for England (Wilkins, Wilson & Brown, 2022) |
| Section 41 Status: | (not listed) |
| Taxa Included Synonym: | (none) |
| UKSI Recommended Name: | Balea (Alinda) biplicata |
| UKSI Recommended Authority: | (Montagu, 1803) |
| UKSI Recommended Qualifier: | (none specified) |
| Red List Citation: | Seddon et al., 2014 |
| Notes on taxonomy/listing: | (none) |
Criteria
| Question 1: | Does species need conservation or recovery in England? |
| Response: | Yes |
| Justification: | The snail is now restricted to a few sites on the banks of the tidal Thames and some of its islands (Aits). Recent anecdotal reports suggest that it maybe down to a very few sites which are subject to 'improvement' and /or impacts of flooding by polluted water. |
| Question 2: | Does recovery/ conservation depend on species-specific actions? |
| Response: | Yes |
| Justification: | This species is restricted to small fragmented habitat patches making it vulnerable to local extinctions, even though its habitat (scrubby waste ground) is much more widespread. |
| Question 3: | At a landscape scale, would the species benefit from untargeted habitat management to increase habitat mosaics, structural diversity, or particular successional stages? |
| Response: | No |
| Justification: | This species would not benefit from untargeted management |
Species Assessment
| Current step on the Species Recovery Curve (SRC): | 4. Autecology and pressures understood |
| Recovery potential/expectation: | Low - Relict or natural rarity |
| National Monitoring Resource: | Opportunistic - insufficient |
| Species Comments: | Maintenance and avoidance of over-management of patches of scrubby waste ground adjacent to the Thames footpath will be of benefit to this species. |
Key Actions
Key Action 1
Proposed Action: Undertake targeted surveys to establish current distribution and status of the species. Key to the conservation of this species is determining where populations are currently present. Once this is known conservation management might be considered as might a re-introduction to other seemingly suitable but as yet unoccupied sites.
Action targets: 3. National Monitoring Plan agreed and implemented
Action type: Status survey/review
Duration: 2 years
Scale of Implementation: ≤ 10 sites
High priority sites: Thames banks and islands between Teddington Lock and downstream to Putney.
Comments:
Key Action 2
Proposed Action: Reintroduce to former occupied sites and consider introduction to additional areas judged potentially suitable. A feasibility study is required to identify potential translocation sites and populations at donor sites and partner organisations e.g. London Wildlife Trust.
Action targets: 6. Recovery solutions trialled
Action type: (Re-)introduction
Duration: >10 years
Scale of Implementation: ≤ 20 sites
High priority sites: Thames Banks, upstream of Putney Bridge to Kew/Syon Park.
Comments:
Key Action 3
Proposed Action: In addition to establishing current distribution under Action 1, assess site characteristics, ownership and management of such sites to inform pressures on species. This analysis could be done as part of a survey.
Action targets: 4. Autecology and pressures understood
Action type: Scientific research
Duration: 2 years
Scale of Implementation: ≤ 20 sites
High priority sites:
Comments:
Acknowledgment:
Data used on this website are adapted from Threatened species recovery actions 2025 baseline (JP065): Technical report and spreadsheet user guide (Natural England, 2025). Available here.