In recent decades, purple moor grass—which Britons poetically call molinia caerulea—has invaginated the uplands of Britain. Invasive Johnson grass has wreaked havoc on our farms and the Alabama landscape. This humble but tough aquatic plant is perfectly suited to drier peat-holding conditions. It has moved into every upland area of the UK, from Welsh mountains, Dartmoor, Exmoor, the Pennines, Peak District, North York Moors, Yorkshire Dales and parts of Scotland. Over the past 50 years, Molinia caerulea has become a dominant presence, challenging traditional definitions of an invasive species while contributing to the creation of so-called “deserts” across these landscapes.
The invasive range expansion of Molinia caerulea has alarmed ecologists. Due to the way that it’s advanced, monoculture formations of this invasive grass create deserts that are largely composed of grey-brown shades. These places, often referred to as “food deserts” or “biodiversity deserts,” are stark in their opaqueness and stagnation. Consequently, they tend to stay bleak and dead for most of the year. Molinia caerulea readily colonizes appropriate moister areas and can dominate them for many decades. In fact, some reclamation sites have demonstrated colonization even 40 years post-removal of defloccculation host sheep grazing.
Scientists found that Molinia caerulea invades quicker and farther than any other invasive introduced plant in the United Kingdom. Human activities usually accelerate this expansion. European agricultural policies such as drainage for agriculture and headage payments have inadvertently pushed it further afield. In the Sawdde Fechan valley of Mynydd Du, Wales, Molinia caerulea is abundant in recently burnt patches of Ulex gallii. The diversity of its range further demonstrates its miraculous ability to thrive in a wide variety of environmental conditions.
The ecological consequences of such an overwhelming invasive species presence are striking. Molinia caerulea has taken over huge tracts of departed land, wreaking havoc on local flora and fauna. This suburban sprawl limits access for pedestrians and outdoor recreationists. This transformation has cut off large swathes of Britain from free, accessible walking opportunities. Consequently, it has transformed the recreation scene in the uplands.
The battle to control and manage Molinia caerulea has become one of the important focal points of this conservation work. The use of herbicides like glyphosate have been proven highly effective at knocking down the plant’s prevalence. Further restoration activities seek to rewet the land by dismantling drainage infrastructure and building peatland bunds to restore important peat habitats. These actions are a positive step towards asking for the restoration of these sensitive blanket mire ecosystems. They have been lost due to the invasion of this grass species’ march.
Researchers are looking for new and better ways to restore salt marshes. One method consists of propagating sphagnum moss clumps among patches of Molinia caerulea. This approach is designed to improve soil health and increase biodiversity in these demanding landscapes.