Progress surveying Carex maritima in 2006

David Pearman

To recap: this is the New Atlas version of the distribution map.

Date Class 3: 22 dots

Date Class 2: 21 dots

Date Class 1: 40 dots

Change Index: -1.37

‘Considerable decline before 1930’

Still there (19)

Gone (12)

Not searched for (16)This was the situation last year, looking at the post-1970 records only

After much diligent searching…

This is what you found…

Last seen 1953

New squares

Last seen 1842

If we draw time-sliced maps using the date classes of the Maps Scheme…

Date Class 0

1500-1929

31 dots

Date Class 1

1930-1969

26 dots

Date Class 2

1970-1986

41 dots

Date Class 3

1987-1999

18 dots

Date Class 4

2000-2009

29 dots so far…

Distribution of Carex maritima in 10km squares

0

5

10

15

20

25

30

35

40

45

1500-1929 1930-1969 1970-1986 1987-1999 2000-2006

Date Class

No

. o

f h

ecta

ds

The current view: a slight decline in distribution during the 20th century, perhaps

How often are new sites found?

Surprisingly, perhaps, new sites (here defined as Wells Sites – 1km squares) have continued to be found at a steady pace since the mid 18th century, and the rate of discovery shows no sign of slowing. This graph ignores any losses.

Number of known Carex maritima sites

020

406080

100

120140

Year: from 1769 to 2006

Cum

ula

tive N

o.

of know

n s

ites

Is Carex maritima moving north?

Probably, yes. In an analysis of 260 records, grouped by 100km northing and evenly divided into four date classes, there seems to be a clear trend towards the north. Is this

climate change, development or ocean currents?

Average northerliness of Carex maritima sites

R2 = 0.9062

7

7.5

8

8.5

9

9.5

1769-1904 1905-1965 1965-1984 1984-2006

Date

Mean n

ort

hin

g (

100km

)

If we add to the Atlas map the new records made since, and remove the introductions on dumped sand by the roadside…

Roughly half of all sites are gone. Mostly on the east coast. Why would these have gone?

Erosion?

Development/agriculture?

Accretion in dune systems?

And why are there seemingly more sites in the west? Just because they were not found before, or because the dune systems there are developing and mobile?

Carex maritima in Orkney

HY55. 1965. ‘In thick vegetation.’ Gone?

HY75. 1981. No-one has looked.

HY44. 1977. ‘Two tiny populations.’ Gone?

HY64. 2003. Abundant.

HY74. 2003. Abundant.

HY53. 1975. Destroyed by airstrip. Gone

HY22. 1883. Has anyone looked?

HY42. 1972. Machair heavily grazed.

HY62. 1979. No-one has looked.

HY21. 2005. Some 51 plants.

HY41. 1968. Introduction on roadside. Gone.

HY50. 1984. Very plentiful. Unable to find since.

ND29. 2005. Thousands of plants.

ND49. 2005. Thousands of plants.

Conclusions

We should keep looking, especially in:-

Orkney

Sutherland

Aberdeenshire

Outer Hebrides

AcknowledgementsThanks to the following for sending records and reports

Brian & Barbara Ballinger, Pat Evans, Lynn Farrell, Ian Green, Alex Lockton, Richard Pankhurst, Walter Scott, Alan Silverside, Paul Smith & Sarah Whild