Boxwood is threatened with imminent extinction in the wild, and faces a number of problems. The first of this arises from the very small extent of the world population, which leaves the only colony very vulnerable to chance catastrophes. It is possible that seed could occasionally be taken and distributed by non-native finches or Mynas (Acridotheres tristis L.), but there appear to be few natural dispersal mechanisms and the chances of spread are low. Attempts to seed individuals more widely on the boulder field have been unsuccessful.
Plants are vulnerable to desiccation and require wet winter conditions to survive to maturity. Rainfall patterns can be highly unpredictable, and persistence therefore depends heavily on the presence of a large seed bank. There are probably tens of thousands of seeds buried amongst the few inhabited boulders, which have accumulated over a number of years. However, there is some concern that this resource may have become depleted recently. Peak germination typically produced 300 seedlings between 2008 and 2010, but fewer than 80 seedlings emerged in 2013 and 2014. The decline may have been partially attributable to heavy seed collection, but also to a succession of poor years for adult survival, resulting in little replenishment. Unfortunately, it is difficult to be certain whether the trends are meaningful, and the downturn may yet lie within the boundaries of normal variability.
It is more certain that the modern Boxwood population suffers considerably from herbivory by introduced insect pests. Plants are often densely infested with aphids and Mealybugs (Pseudococcus spp.). These in turn attract predators such as hoverflies and ladybirds (Cryptolaemus montrouzieri Muslant) which may help to limit the infestations. However, the plants usually sustain obvious signs of impairment and appear to experience considerable mortality as a result. A further threat could come from Spider Mite (Tetranychus spp.), which has not yet been detected in the south of St Helena but is already prevalent in the gardens in Jamestown, where it attacks and kills cultivated Solanaceae species and can be very difficult to control.
Invasive weeds present a less serious threat, although species such as Lantana (Lantana camara L.), Tree Tobacco (Nicotiana glauca Graham) and Wild Mango (Schinus terebinthifolia Raddi) are widespread in the locality and could overgrow the Boxwood patch. Periodic weeding by conservationists has probably kept the problem under control thus far. In addition, there are a number of other introduced annual and perennial herbs scattered across the dry coastal hills of St Helena which act as hosts for Mealybug, and probably represent a more substantial management problem.
A large part of the historical loss was a likely consequence of the huge goat population (Capra hircus.) which built-up on St Helena following their release by Portuguese mariners in the early 1500s. These are widely thought to have devastated the vegetation of dry coastal areas over the following centuries. The Goats have now been almost eradicated, but rabbits (Oryctolagus cuniculus) remain widespread and efficiently destroy seedlings of many species.
Ultimately, the decline of the Boxwood may have been largely a result of an inability to cope with introduced pests, competitors and diseases, against which most of the arriving non-native flora has some resilience. However, the loss of vigour which appears to have occurred since the 1800s seems extreme, and is difficult to explain. It may be a result of inbreeding amongst the tiny population, greatly reducing the gene pool and causing associated health problems. Melliss noted that the leaves had a strong scent, whereas modern plants often have little. This may indicate a declining ability to produce the toxic alkaloids which confer protection against many herbivores. It is therefore not necessarily the case that Boxwood is intrinsically a ‘weak species’, and could have fared better had it survived to the modern era of conservation in greater numbers.