“Sloping rocky banks and red sandstone cliffs. Extinct.” This is the brief and rather depressing entry for Purple Oxytropis Oxytropis halleri in my old Flora of Angus book (Ingram and Noltie, 1981).

The plant has been gone from Angus for a long time, as it has from North Queensferry and several other locations in Scotland. It’s one of our rarest wildflowers.

Purple oxytropis – a relict

Purple oxytropis is an impressive plant – a member of the Fabaceae (legume) family, with purple flowers, silky leaves and growing in sometimes large colonies in the few places where it does still exist. In the UK, the species is only found in Scotland. Elsewhere, it’s only found in the high mountains of central Europe.

Its Scottish distribution is described as ‘relict’. Most of its remaining populations are coastal, with its stronghold on the north mainland coast. There are a very few populations on the north-east coast, and one extremely isolated population away down on the Mull of Galloway, in the south-west. It’s also found near the summits of three Scottish mountains, two in Perthshire and one in Argyll.

So why is it so rare?

It’s likely that it was never a very common plant, and this country is very much on the northern edge of its range. But there’s no doubt that it was more widely distributed in the past than it is today. Some populations have been lost due to development destroying its habitat. The species is vulnerable to over-grazing– it’s tasty to grazing animals (of which we have an increasing number in Scotland). It also likes open conditions, so won’t thrive in areas that get too encroached with scrub or trees.

Purple oxytropis is dependent on pollinators, mainly bees, to successfully reproduce. Anything impacting on these pollinators will in turn impact on the ability of purple oxytropis to survive.

Its remaining isolated coastal populations are also extremely vulnerable to the impacts of climate change. Rising sea levels could be catastrophic, and associated erosion could spell disaster. The species isn’t widely distributed enough to withstand local impacts like this. A recent study carried out for Plantlife concluded that it is probable that the Mull of Galloway population will become extinct if no new plants appear and highlighted the threat that a single event such as a landslip could have on the fragile population there.

The isolated nature of the remaining populations means that the plants are likely to exhibit low genetic diversity and high levels of inbreeding, which will weaken them and make their future survival less likely. However, We don’t know enough about the genetics of the species to be sure.

Does any of this matter?

How much should we care about trying to save a species which is already on the edge of its range? Surely, it’s doing okay in the Alps? The problem with that argument is simply, where do you draw the line? If we lose it from Scotland, does the next closest population become the ‘edge of range’ one which it’s OK to lose? And then the next?

If we want to live in a country that’s rich in wildlife, we must look after the species that make their home here. The problems facing Purple Oxytropis are difficult but not insurmountable. And by tackling the problems facing this species, we will also address these problems for a host of other species which are facing similar threats.

Looking at a map of Purple Oxytropis distribution over time is like watching a series of lights blinking out one by one. I don’t think anyone wants the map to go completely dark. It’s up to us to keep as many lights on as possible.

Plantlife is taking action for Purple Oxytropis through Species on the Edge partnership.