BSBI long colour

Distribution maps of plants

>> BSBI Hectad Maps: 10km square distribution maps showing distribution in standardised time slices. Data is about 2 years old and is partially checked. It is good for showing recording levels in counties.

>> BSBI Tetrad Maps: 2km square distribution maps showing distribution in standardised time slices. The distribution of axiophytes is particularly interesting at 2km scale.

>> BSBI Big Database: 10km or 2km distribution maps, completely up to date but only partially checked and therefore containing many errors. With permission, you can see the full details of each record.

>> NBN Gateway: distribution maps of all plants and animals at 10km resolution (or up to full details if you have access permission). The data is drawn from a number of sources, not just BSBI.

>>NBDC website: the equivalent of the NBN in Ireland. You don’t have to apply for permission to get full details of records.

>> New Atlas: a website hosted by CEH which gives distribution maps from the BSBI Atlas. NB, these are the only checked maps and are the best to use if you want to avoid errors appearing, although they are 15 years old.


The BSBI Distribution Maps Scheme

Launched in 1950, it is one of the world’s longest-running natural history distribution mapping projects. It is constantly updated and improved by the BSBI’s networks of volunteers, county recorders and referees, and it is always in use by scientists, conservationists and governmental bodies for determining the abundance, range and changes in the distribution of vascular plants and charophytes in the British Isles.

How it works

In the 1940s the Ordnance Survey plotted a grid across the whole of Britain based on km squares. There are some 3,000 10km x 10km squares in this grid, which are given codes such as SX45 or NO66 (S is for the southern 1000km square, N for the northern one), as shown on the map below.

For full details of the national grid, visit the Ordnance Survey web site.

The British National Grid


Equivalent grid systems have since been created for Ireland and the Channel Isles.

Irish grid



Distribution maps

These are created by recording which species are found within each square of the national grid. The first Atlas was produced by the BSBI in 1962, showing black dots for records since 1930 and open circles for older records.

Since then there have been numerous similar maps published, most notably Scarce Plants in 1995, and the New Atlas in 2002. These plotted current records (‘black dots’) as those made after 1970 and 1987, respectively. Thus there are four traditional date classes for recording plants, as follows:

  • DC0 = -1929
  • DC1 = 1930-1969
  • DC2 = 1970-1986
  • DC3 = 1987-1999
  • DC4 = 2000-2009
  • DC5 = 2010-2019

From now on we plan to record in decade-long date classes, so Date Class 6 will be 2020-2029. Another innovation is the change from 10km squares to 2km squares for recording units, which is increasingly coming into use; but, although these use the same date  classes, those are not mapped because it would be impossible to achieve realistic levels of coverage.

Tetrad Maps

A tetrad is a 2km x 2km square, given a letter code as shown below. So tetrad SW41A is made up of the four 1km squares SW4010, SW4011, SW4110 and SW4111.

Tetrads within a 10km square

-- The DINTY system for tetrads --


The Distribution Database

The BSBI now operates a Distribution Database as a central store for all our records of plants and charophytes. It contains some 15 million biological records (November 2010) and is expected to grow to twice that size in the next year or two. It is updated frequently from our network of Mapmate recorders and from other sources such as herbarium digitization projects.


The database gives all records in full detail and is fully editable by users. Because this is research level, live, data it is not appropriate for the general public or for consultancies. Filtered, interpreted data can be obtained from your local records centre, the NBN Gateway and other public sources.

BSBI county recorders, referees and other approved users are given password to access the database. If you think you have a legitimate reason to access it, please contact Kevin Walker or Alex Lockton.

>> Go to the Big Database


Taxonomy Database

Visit the BSBI’s taxonomy database, which gives plant names and their synonyms, chromosome numbers and details of much literature relating to british plants.

>> Go to the ‘Leicester’ Database


Vice counties

The system of counties and vice counties was devised in the 1870s to create 113 units of roughly equal size covering the whole of Britain (the process was later repeated in Ireland). The boundaries of the vice counties do not change with political reorganisation so have remained the same ever since. Click on the link below for a handy web page showing the vice counties.

>> vice county boundaries (Britain only)