Introduction
The 'humble bumble' (Bombus humilis), together with
about half of the British species of bumblebee, has suffered
a drastic decline in range in recent decades. Its conservation
is addressed nationally by a UK Species Action Plan. The
humble bumble is somewhat smaller than the common garden
bumblebee (B. terrestris), and has a fairly uniform,
golden colour.
In London as a whole the species is rare, though it remains
widespread in suitable habitat along the East Thames Corridor,
especially on the Essex side. The humble bumble has been
recorded from the London Boroughs of Barking and Dagenham,
Bexley, Newham, Tower Hamlets and Havering and most records
are from flower-rich wasteland near the tidal Thames. As
the species is absent from some apparently suitable sites
further inland, coastal influence is likely to be a key
element of its habitat requirements.
Bombus humilis has no universally-accepted English
name. One translation of its specific name from the Latin
is 'humble bumble', hence the name we use in this Statement
for the sake of convenience. The bee is a member of two
groups of species known as long-tongued bumblebees and carder
bees.
Distribution and Requirements
The decline in the humble bumble's range throughout the
20th century, where it had disappeared from most
of its northern and inland sites by the early 1960s, has
been attributed to habitat loss through the development
of modern agricultural practice. The mechanisation of hay-making
and, later, the shift to silage making, has resulted in
a restricted distribution, now concentrated mainly on the
East Thames Corridor, south-western coasts of England and
southern coast of Wales.
Both nationally and in the London area, the changes in
population and distribution of the bumblebee have been like
a 'miner's canary', reflecting significant rural and urban
environmental changes over the last half-century.
The humble bumble is associated with flower-rich habitats,
but uses a surprisingly restricted range of species for
foraging, notably certain perennial, deep-rooted members
of the pea and dead-nettle families. The right combination
of conditions is usually found in London's wasteland sites,
otherwise known as 'post-industrial wasteland'. These sites
are usually unmanaged and are often characterised by their
sandy substrates, open conditions and low nutrient status.
This bumblebee appears to be able to survive on long, narrow
mosaics of habitat better than other threatened bumblebees.
However, the bee's nesting density is low so it needs a
large area of land to support a viable colony. Narrow habitat-mosaics
are unfortunately particularly vulnerable to fragmentation.
Conservation Considerations
In East London, the decline of the humble bumble is overwhelmingly
the result of wasteland loss to development. The continuing
pressures to develop on such sites constitute by far the
greatest threat to the species in the London area · particularly
at its Thames-side locations.
Habitat management can be of benefit in some cases, particularly
on sites whose clay substrate and higher nutrient status
encourages plant growth. In these areas, phased removal
of vegetation on a long rotation, or disturbance management,
is essential to prevent the development of a sward dominated
by false oat-grass, which crowds out the bumblebee's wildflower
foraging resources. Regular or frequent cutting, however,
can be catastrophic.
Future Actions
There are five broad actions that could benefit the humble
bumble. Most of these are inter-dependent.
Survey, monitoring and research Survey
work is required to assess the bee's distribution and population
more accurately. This should be targeted at those sites
under greatest threat of development. Monitoring is also
required on known sites, to answer questions about natural
fluctuations in the species' populations and their response
to environmental variables other than development and direct
disturbance. Also, the absence of the species from some
apparently suitable habitat raises questions about its nesting
requirements, foraging behaviour, minimum viable area and
range. Answers to these questions will help to assess whether
a population could survive if a site were to be partially
developed.
Raising awareness of wasteland biodiversity
The humble bumble has no legal protection, though its status
as a UK Biodiversity Action Plan species is an important
consideration. As the humble bumble is part and parcel of
issues surrounding the conservation of wasteland, linking
it to habitat action will strengthen the case for its conservation.
As a member of one of the more popular groups of insects,
the plight of this bumblebee should be used as a flagship
in raising awareness of biodiversity, and social and landscape
values of wasteland.
Reviewing the GLA's site evaluations
Most of the GLA's ecological sites are acknowledged in Unitary
Development Plans (UDPs) through designation as Sites of
Nature Conservation Importance (SINC) or equivalent. The
degree of protection of sites in UDPs is, to a large extent,
dependent on this status and improved survey data may justify
re-evaluating for some sites. Reviews should be prioritised
in accordance with the timetable for the review of UDPs
themselves.
Protecting wasteland habitat A
wasteland site's status as a SINC could help to justify
a Section 106 Agreement to manage a site for its nature
conservation benefit. This management should be guided by
the foraging requirements of the humble bumble where the
bee may be present.
Managing more nutrient-rich sites
Whilst these, too, may be threatened by development,
the risk is that these sites will become so dominated by
false oat-grass that they will lose the habitat resources
that the humble bumble depends on. As noted above, management
would therefore be required.
Further Reading
Benton, T (2000). The Bumblebees
of Essex. Lopinga Books, Wimbish.
Chapman, R (in prep.). The
Foraging Ecology and Conservation of Bumblebees in Urban
Areas. Institute of Zoology/University College, London.
DETR (1999). Bombus humilis
(a carder bumblebee). UK Biodiversity Group Tranche 2 Action
Plans. Volume IV · invertebrates.
Williams, PH (1986). Environmental
change and the distribution of British bumble bees (Bombus
Latr.). Bee World, 67: 50-61
Williams, PH (1989).
Distribution and decline of British bumble bees. www.nhm.ac.uk/entomology/bombus/decline
Contact
The contact for this Statement
is the Greater London Authority
