Juniper has declined across Britain but the problem is particularly acute in the low chalk downland, where it has been lost completely from 9 of its 27 lowland vice-counties, including North Devon and North Somerset. Populations that are still surviving in Wiltshire have shown declines in juniper abundance of 44%. Many colonies have dwindled to such an extent that they are functionally extinct. Of our south-west populations there are some small extant populations in Gloucestershire; from what I’ve seen of the Dorset populations each is down to just 2-3 male trees - male trees naturally live longer than female trees; a male tree can live more than 2000 years; where the females had failed to reproduce and died-off years ago. The species is dioecious, with male and female cones on separate plants so requiring wind pollination of closely grouped trees to transfer pollen from male to female cones. The Dorset males are as good as extinct without human intervention. The only south-west county with multiple sizeable populations is Wiltshire. But when I say "sizeable" I mean in comparison, as the Wiltshire populations are rapidly declining just the same.
Today’s heavily managed countryside has little in the way of suitable habitat for juniper. Annual cycles of grassland management conflict with its reproductive strategy and, despite its prickly foliage, juniper is often damaged by livestock, rabbits and deer, with its seedlings particularly palatable.
As chalk downland junipers typically live for hundreds of years, they have hundreds of opportunities to reproduce successfully. If each individual is survived by just one offspring, a stable population will result. For this reason, and because of juniper’s tendency to reproduce episodically, the absence of seedlings at a site for a decade or more should not be a cause for great concern. However, today many populations consist entirely of old collapsing bushes which are prone to sudden die-off. Urgent intervention is clearly needed at such sites.
Juniperus communis is declining in other parts of lowland Europe. Computer modelling suggests that its European range will contract northwards as the climate warms, implying a greater international responsibility to conserve its populations in the UK. An emerging concern in Britain, is the trend for increasingly mild winters which may eventually result in a failure to break seed dormancy (juniper seed requires two hard-cold winters to germinate). Furthermore, young seedlings are highly susceptible to summer drought on the poor chalk downland soils.
As a pioneer species, the proximity of bare ground appears to be the most important factor responsible for seedling establishment. Areas that remain continuously open with plentiful bare ground are much more likely to support seedlings. Episodes of intense bare ground creation need to be followed by long periods of little or no disturbance. Traditional activities such as droving, shepherding would have created such conditions. Similarly, ancient trackways, earthworks and old quarries provided ideal habitat and are typical juniper haunts today.
Juniper is almost a habitat in its own right, supporting an impressive range of wildlife, including some species that could not survive without it. Juniper berries and shoots provide a food source for wild birds and mammals, especially during autumn and winter months and it supports over 50 insects, such as the juniper shield bug, juniper aphid and juniper carpet moth. Juniper also provides ideal habitat for spiders. Studies show that the larger the populations of juniper, the greater diversity of insect species. In addition, over 40 species of fungi are either entirely or partially dependent on juniper, and its stems and branches can support a range of lichens and bryophytes.
Trebrown Nurseries is building on the Plantlife action plan. Their guide contains detailed advice to aid the recovery of Juniper across the chalk and limestone country of lowland England. We are creating our own seed stands on the farm, and we are growing wild-sourced south-west seed in the nursery. Juniperus communis is not a FRM controlled species, but is certified under the voluntary FRM scheme.
