30 Days Wild – Day 28

A really blustery day spent at home, mainly in the garden. The conditions meant the moth trap had few visitors and photographing insects on waving flowers was a near impossibility.

The highlight was a male Cheilosia caerulescens, a hoverfly I first saw last year and which was only first found in the UK in 2006. It is one that probably came here in plants transported for the horticultural trade. The larvae mine the roots of house-leeks and were probably in the roots of imported plants. It was first found in Surrey and is now quite widespread in S. England.

Cheilosia caerulescens 4x3

Cheilosia caerulescens

Although this species may not do too much harm, unless you are an avid grower of house-leeks, it does illustrate how difficult it is to keep from inadvertently bringing species into the country. With increased travel and much more international trade the opportunities for stow-a-ways are many.

Introduced species can be a hot topic, with widely differing views about what controls there should be. My personal feeling is that wherever you stand on the rights or wrongs of controlling invasive species, bringing ever more in should be seen as a bad idea. Any newly arrived species is unlikely to be adapted to the environment and so most die out. If they don’t they will be competing with species already present, there are not generally lots of unused resources lying around, something will be using them and any arrivals will effectively be taking away resource from something else already using it. In the worst cases they thrive to the exclusion of lots of other species, especially if there is no local control by predators, parasites or disease to keep them in check as would be likely in the native range. The upshot of this is that we tend to gain widespread generalist species and lose localised specialist species, in short the species diversity is reduced and some of the variety that makes the world so interesting is lost. This is happening worldwide of course and the impact of introduced species is one of the greatest extinction threats to local wildlife faced across large areas of the world.

As I mentioned I spent most of the day in the garden and many of our garden plants are  a good fit for potentially invasive species. Most are not native to the UK and many not to Europe, but they are selected to be types that will grow here, and the ones we grow most often are the easiest to grow, which is to say they grow very well here. All characteristics that would make a successful invasive species. A lot don’t grow well from seed for one reason or another, but some will set viable seed and a good few will grow well from roots or rhizomes, which is why fly-tipping of garden waste can be sure a problem and  a major route out into the countryside for garden plants.

I have been refurbishing my pond over the lockdown period and it is beginning to look a lot better, with several plants coming into flower, including water forget-me-not and lesser water plantain.

water forget-me-not

water forget-me-not

lesser water plantain

lesser water plantain