Juniperus bermudiana

From the time that Bermuda was first colonized in 1609 Juniperus bermudiana has been used extensively for construction purposes and as fuel for cooking. The use was so extensive that by 1622 special legislation had to be introduced (Tucker 1970) to control the export of the island’s most dominant tree species. Between 1693 and 1878, the Bermuda legislature passed sixteen further acts in order to restrict the uses of the juniper. Despite these Acts, the ship-building industry eventually denuded much of Bermuda's landscape by the 1830s. The decline of the ship building industry after 1900, combined with the replacement of  local juniper timber for construction with cheaper imported timber from the U.S. and rural electrification, which precluded the need for wood as  cooking fuel, enabled a full recovery by the early 1940s. However, it was once more devastated as a result of the accidental introduction of two coccoid scale insects in 1946 (Challinor and Wingate 1971).

The juniper scale (Carulaspis visci) and the oyster-shell scale (Lepidoscaphes newsteadi) were present on ornamental species of juniper which were shipped to the island from California, USA (Bennet and Hughes 1959). In the absence of natural biological controls and genetic traits for resistance the native J. bermudiana suffered rapid defoliation and death, reducing the population by 95% within a period of 10 years (Wingate 2001)

During the following decades the bare landscape was reafforested using exotic species. Casuarina equisetifolia was especially favoured for its rapid growth. Invasive broadleaf plant competitors (which create too deep a shade for seed germination or growth), are now by far the greatest factors limiting the junipers distribution and self-seeding potential. Likewise, germination of the naturalized Ficus retusa in rot hollows of old junipers (which leads to eventual overshading and strangulation) and overshading by taller growing invasive broadleaved trees, especially in sheltered valley situations, is now the major cause of adult mortality.

To add to the problems, J. virginiana and J. virginaina var. silicicola have been introduced to Bermuda from Florida, USA. Both taxa are resistant to the scale insects. They readily hybridize with J. bermudiana causing a depletion of the germplasm through hybridization and introgression (Adams and Wingate 2008) .

Urbanisation is also a problem. Today Bermuda is recognised as one of the most densely populated isolated oceanic islands in the world with a mean human population density of five per acre and one third of the country is totally urban (Wingate 2001). About 20% of Bermuda's land area is now paved over with roads, parking lots, buildings and industrial yards. This trend is likely to continue unabated.

Although chemical control of the juniper scale was possible, it was avoided for safety reasons due to the high density of the human population. As a result of rapid natural selection of a trait for scale resistance, which must have survived in about 5% of the population, most seedlings now seem to be partly or totally immune to scale attack, and survive. This enabled intensive re-forestation efforts to begin about 1980 and the species has since recovered to approximately 10% of its former population density in managed parkland and garden habitat. (Procter and Fleming 1999, Wingate 2001)

Juniperus bermudiana is cultivated in gardens outside of Bermuda and some of this material has potential to supplement restoration programmes in Bermuda. Perhaps the biggest planting is in St Helena and on Ascension Island where seed was introduced during the mid-19th century to establish timber tree plantations (Adams 2008). Ironically on these islands J. bermudiana is now becoming an invasive problem. Juniperus virginiana has also been introduced on St. Helena so there is the potential for hybridization (Adams 2008).