One of the major threats facing St Helena’s cloud forest arises from the widespread encroachment of invasive non-native weeds through areas of native habitat. Jellico is a robust species which is clearly better able to compete with tall, vigorous incomers than many of St Helena’s endemic plant species. However, it is unlikely to displace invaders from areas they already occupy, and as the seed has no specialized dispersal mechanism it is likely to be slower to colonize new gaps than species such as Whiteweed (Austroeupatorium inulifolium (Kunth) R.M.King & H.Rob.), New Zealand Flax (Phormium tenax J.R.Forst. & G.Forst.), Blackberry (Rubus pinnatus Willd.) and Bilberry Tree (Solanum mauritianum Scop.). As a consequence, there is a risk of gradual, long-term decline, especially since some of the existing strongholds are prone to land slides which could periodically damage the existing vegetation cover. Damp areas may also be colonized by pasture grasses which dry the soil and remove germination niches.
Since the most vigorous colonies are associated with damp ground, there is also a concern that their ability to compete with invasives will decline if there is a sustained reduction in water flows in the Peaks. There are currently no data to evaluate this and no climate change predictions have yet been developed for St Helena. However, some residents believe that catchment volumes have decreased, perhaps as a result of the loss of cloud forest and the associated reduction in water retention capacity. Many of the gullies of the Central Ridge that may once have provided suitable habitat are now densely choked with non-native vegetation.
A more immediate threat stems from herbivory by rats (Rattus rattus and R. norvegicus). These introduced species are now abundant pests throughout the Peaks area, and may eat the stems of Jellico. Outbreaks are sporadic but may cause substantial local damage. The problem is usually suppressed by baiting programmes initiated by conservation workers, and once the offending group of herbivores have been destroyed it may be some time before the behaviour is learned again.
A final possible threat is posed by hybridization with the closely-related Small Jellico (Berula burchellii (Hook.f.) Spalik & S.R.Downie). A large monocultural patch of plants at High Peak exhibits intermediate characteristics between the two species, and similar phenotypes have been reported in the north of the Diana’s Peak range, on the slopes above Wrangham’s (Cairns-Wicks 2003). The identity of these plants has not been confirmed, but it is likely that they are of hybrid origin. If so, it is not clear how much of a threat is posed. Cronk (2000) reported that the species seemed to have little cross-fertility in cultivation, and thus it may be very rare for spontaneous hybridization to develop. However, the intermediate genotype is clearly able to reproduce and may become more of a concern should it spread more widely. Further back-crosses could dilute the integrity of either parent species.