or massive decline , as here:
This once widespread butterfly has undergone a massive decline in its range and is now only reported from the County Down coast.

...
: Northern Ireland's Priority Species & Species of Conservation ...
Throughout the United Kingdom, since the 1970s, this butterfly has undergone a dramatic and severe decline. Once considered widespread in Northern Ireland ...
www.habitas.org.uk/priority/species.asp?Item=5574

asia « Exit Stage Right
According to MARD, the major reason for their dramatic decline is poaching. .... as 50000 in its range, which includes Mongolia, Uzbekistan, Turkmenistan, ...
exitstageright.wordpress.com/category/asia/

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Note added at 1 hr (2009-02-05 11:27:32 GMT)
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The Xerces Society » Conservationists Seek Federal Protection for ...
12 May 2003 ... The butterfly has been wiped out of much of its range in ... of prairie to cropland is the primary reason for the butterfly’s decline. ...
www.xerces.org/2003/05/12/conservationists-seek-federal-pro...


A-Z of butterflies - Butterfly Conservation
This small butterfly is found mainly in heathland where the silvery-blue wings of the males ... It has undergone a major decline through most of its range. ...
www.butterfly-conservation.org/Butterfly/32/Butterfly.html?...

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Note added at 1 hr (2009-02-05 12:05:32 GMT)
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or distribution range

3 s.m. TS biol., in biogeografia, zona di insediamento di un animale o un vegetale

http://old.demauroparavia.it/8135

South Dakota Ecological Services Field Office: American Burying Beetle
18 Sep 2008 ... In the 1980s, entomologists documented the decreasing abundance of the American burying beetle across its range. ...
southdakotafieldoffice.fws.gov/BEETLE.HTM

IATE

areale naturale
Reliability 3 (Reliable)
Term Ref. Accademia italiana di Scienze forestali
Term Note può essere "continuo" o "disgiunto",cioè comprendente regioni separate;l'areale artificiale considera la zona in cui l'organismo è stato introdotto dall'uomo,l'areale potenziale considera anche le regioni in cui l'organismo può diffondersi p.es.se venisse coltivato
Date 24/09/2003

the geographical and elevational limits within which an organism occurs naturally
Definition Ref. Helms,John A.,The Dict.of Forestry,1998,Soc.Am.Foresters

Term natural range
Reliability 3 (Reliable)
Term Ref. Helms,John A.,The Dict.of Forestry,1998,Soc.Am.Foresters;Ford-Robertson,Soc.Am.Foresters
Term Note ecology;REF:Ford-Robertson,Soc.Am.Foresters

area di distribuzione
Reliability 3 (Reliable)
Term Ref. Haensch/Haberkamp,Diz.agricoltura,1963,voce 4851
Term Note Botanica generale
Date 24/09/2003

Term areale
Reliability 3 (Reliable)
Term Ref. Haensch/Haberkamp,Diz.agricoltura,1963,voce 4851
Term Note Botanica generale

range of distribution
Reliability 3 (Reliable)
Term Ref. Haensch/Haberkamp, Dict. Agriculture
Term Note General Botany

Distribution and
decline of
British bumblebees
.... Consequently, in regions nearer the edges of its distribution range, a species may be more locally restricted to just those habitats with most food (Williams, 1985a, 1988, Williams et al., 2007 [pdf]).
http://www.nhm.ac.uk/research-curation/research/projects/bom...

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Note added at 2 hrs (2009-02-05 12:55:56 GMT)
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or steep decline

National Audubon Society - Birds in Decline: Lark Sparrow
Threats: In the eastern part of its range, the Lark Sparrow is threatened ... But the fact that its population has experienced such a steep decline in four ...
stateofthebirds.audubon.org/cbid/profile.php?id=13

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Note added at 1 day1 hr (2009-02-06 12:00:27 GMT)
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on reflection, you could also say shrink or shrinking

Unique long-term butterfly records
make British butterflies one of the best
studied groups in the world. We know
that in the early 19th century the comma
butterfly was widespread throughout
Britain, but something happened at the
beginning of the 20th century that caused
the comma’s range to shrink until it could
only be found along the border between
England and Wales. What caused this
dramatic fall?

www.nerc.ac.uk/publications/planetearth/2006/summer/sum06-b...

Among our native butterfly species, the most common pattern of change, unfortunately, is shrinking ranges as suitable habitat disappears...
http://www.cbif.gc.ca/spp_pages/butterflies/geography_e.php

EXTINCTION NEWS
He said dramatic drought-induced changes in the Southwest landscape since .... 95%-- and its range has shrunk from continent-wide to isolated strongholds in ...
www.geocities.com/~gaiachurch/xtinct5.html

Status Survey and Conservation Action Plan Parrots Edited By Noel ...
Butterfly ranching, however, has two unusual characteristics: (1) It is often ..... coastal strip of south-west Tasmania and its winter range has shrunk to the east of the ..... Kakapo have a slow and often erratic reproductive rate with four and five ...... The ensuing drop in numbers and range has been dramatic. ...
www.parrots.org/publications/pap/parrotactionplan.txt

e.g. its range in Europe has shrunk dramatically

Spain - Realm of the Iberian Lynx
Today, its range has shrunk dramatically to just two viable (but isolated) ... within the Coto Doñana National Park, one of the finest wetlands in Europe. ...
www.naturetrek.co.uk/wildlife-holidays-in-europe/detailsdb.... - 26k -