Small-flowered tonella (Tonella tonella) COSEWIC assessment and status report: chapter 8

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Limiting Factors and Threats

The most immediate threat to Tonella tenella in British Columbia is habitat destruction through a housing development on waterfront private property. Previous owners had plans for a residence on the site but these did not materialize. In recent years Saltspring Island has shown a marked increase in housing development with waterfront property at a premium. The population of Saltspring Island has increased by 78% between 1986 and 2001 and further projections indicate a further increase of 43% by 2026 (Linda Adams, Islands Trust, pers. comm., 2003).

Suppression of both natural and human-induced fires in the last century may also have an effect on the survival of T. tenella. The vegetation in this region would naturally be maintained by fires, however, in their absence, high fuel loads build and catastrophic fires could result. During the past few years, drought conditions have led to numerous fires in British Columbia. The site on Saltspring Island is certainly susceptible to a wildfire that could possibly remove T. tenella completely. Even if the plant survived a wildfire, changes to the habitat might prove unfavorable for T. tenella.

Introduced species are also a problem at the site. The vegetation characterizing the T. tenella site has been altered with the introduction of European species. Although a large number of native forbs occur in these areas, much of the vegetation is dominated to a large extent by introduced species, particularly grasses, including a number of species of Bromus.