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Natural History of Scilly

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Timeline: wildlife arrivals and introductions

25,000 BC - Surviving the Ice Age

Ice Age: Scilly, Britain and mainland Europe were joined. The ice sheet reached northern tip of Scilly. (For geological evidence of glaciation and tundra conditions in Scilly, visit the Geology Tour page). Grasses, sedges, lichens, the dwarf pansy and other tundra wildlife thrived in the arctic conditions. There is good DNA evidence that one endemic species, the St Martins Ant, dates back this far. Whether the Scilly shrew is also an Ice Age relic is still a mystery; it may, like many species unable to live in these cold arctic conditions have survived in refugia further south. 

Academic article on shrew refugia and dispersal

DNA investigation into the story of the St Martins Ant

17,000 BC  Wildlife returned as the ice receded

As the climate warmed, some species returned across the land bridges from their refugia in southern Europe. Species spreading north to that part of the landmass that was to become Scilly included field grasshoppers, meadow brown  butterflies and oak trees. (For more on DNA analysis of Pleistocene and post-glacial biogeography, see Schmitt 2007 and Petit et al 2002 'Identification of refugia and post-glacial colonisation routes of European white oaks').

10,000 - 5,000 BC Sea levels rose, isolating the Scillonian landmass

Sea levels rose, the Scillonian landmass became cut off, first from mainland Europe and then from Britain, possibly as early as 10,000 BC. Marine wildlife and salt-tolerant plants colonised the shores. Most of the islands were joined together and much of the Scillonian landmass was wooded. Remnants of a submerged forest have been seen on the sea bed between St Marys and Samson. Evidence of a transition from herb-rich grassland to mixed deciduous woodland comes from analysis of intertidal peaty deposits at Porth Mellon, St Marys and Par beach, St Martins (Scilly Historic Environment and Research Framework). At this time, Britain was still linked to mainland Europe through Doggerland, now Dogger Bank, in the North Sea.


5,000 BC Humans settled in Scilly, farming and exploiting the local wildlife

Neolithic human settlers arrived in Scilly, bringing sheep, goats, cattle and grains, clearing some of the woodland and eating the wild deer. 

43 - 410 AD  Romans arrived and sea levels continued to rise

Rising sea levels divided Scilly into the group of islands seen today. Romans arrived in Scilly and introduced the European rabbit into Britain. The earliest record of rabbits in Scilly  is dated 1136 AD

1500s Wool aliens introduced

From late medieval time, many plant species ‘wool aliens’ arrived in Britain as seeds entangled in the fleeces of Spanish Merino sheep. Compact brome and Cretan mallow are probably wool aliens. Although described in the Biological Records Centre as introduced to cultivation in 1723, the Cretan mallow is listed in Lousley's census of wool aliens, and its distribution around ports mills and factories supports its unintentional introduction in imported sheep fleeces.


1830s - present  Sub-tropical plants introduced

The Smith family brought botanical specimens back from California, South Africa and New Zealand to plant on Tresco. Many of these plants, such as Monterey pine, Agapanthus, Pittosporum and Hottentot fig, and some stowaways such as Stick insects have naturalised in Scilly.

1950s Pacific seaweed introduced

 Pacific seaweed Sargassum muticum is accidentally introduced, allegedly on American seaplanes.

Identifying seaweeds- the Natural History Museum Big Seaweed Guide >>

1950s and 1960s Avian colonisers


Starlings and Collared doves arrive and breed in Scilly.

1980s Hedgehogs introduced

Hedgehogs were introduced on St Marys, posing a threat to ground-nesting birds whose eggs they eat.

2010s Red squirrels introduced

Red squirrels were introduced on Tresco, it is possible that red sqirrels lived in the woodland that was Scilly before human settlers arrived in Neolithic times  in which case this is a reintroduction. 

In 2014, Brown rats were eliminated from St Agnes, allowing Manx shearwaters to breed successfully.

Little Egrets about to colonise?

Little egrets have been seen in Scilly in increasing numbers over the last 10-15 years and may breed here soon ....

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