My week, or at least the three days of it that have passed so far, has been dominated by aliens. These have not been little green men, although some have been green, some small but others very definitely not.
I came straight back to the government agency fera on site from dawn culling ruddy duck, these ducks came from North America and escaped, ironically, from the Wildfowl and Wetlands Trust at Slimbridge. The government decided to try and eradicate them from the country, a brave decision, both because eradicating any species is very difficult indeed and because it is a less than universally popular thing to be doing. For the reserve it means trying to minimise the impact on other species and visitors and hoping that they do a "good job" so they do not need to come back.
The same morning we had one of our twice yearly meeting of the partners who run the Blashford Lakes reserve, at which one of the issues was the "favourable condition" of the reserve. This is a status assessed by Natural England and is designed to ensure that designated wildlife sites remain good for wildlife. Unfortunately having aliens species can be one thing that means the assessment will go against us. In this case the offending species are Crassula helmsii and common carp. The first is a plant from Australia introduced for garden ponds, but thrown out when it became too abundant and now widespread in ponds and lakes in the countryside. With changes in the chemical control that is allowed there is now very little that can be done to control it and so we are no longer so seriously "marked down" for having it on site. The carp are a different matter, they are alien, although they have been in Britain for hundreds of years. We have one lake where they have bred in such numbers that we have now been told they have to be reduced in number to restore the bird population of the lake. This will be a difficult process, not just because of the practically problems but also because of the number of interests involved.
The picture shows Crassula growing amongst native plants in an area where we are trying to reestablish a fen and reedbed habitat. The Crassula is the green background plant with tiny leaves. If we did spray the unwanted Crassula here we would kill off all the native plants as well. What we don't know is if the Crassula will prevent the native fen flora from establishing.On Tuesday afternoon I went out netting the edges of Ivy Lake and Blashford Lake in search of the "Killer shrimp". This is a species is similar to our native freshwater shrimp, but about three times the size, so far it has only been found in Grafham Water, Cambridgeshire. It has come in from Eastern Europe and is a small but aggressive predator. The worry is that by changing the balance of species at the lower levels of the food chain this will have knock on effects on everything else, it will have an effect, just how much and on what scale only time will tell. In this case eradication seems out of the question, so trying to prevent spread is the main response. It seems certain this species arrived by accident, possibly in the bottom of a boat.
Wednesday came around and in the evening we hosted a meeting about wels catfish, a species from eastern and southern Europe. They can get really big, perhaps 2.5m long, although so far usually more like a metre or so and twenty or thirty kilos in this country. They eat all sorts of things including fish, crustaceans and even birds. They can and do breed in this country and climate change is only likely to make things better for them. This species was legally imported into the country to certain lakes, but people have moved them from the original sites to other lakes without permission. The impact of this remains to be seen, although it seems one of the favourite prey species is the American signal crayfish, another alien introduced into fish farms which has got out over the fence. The signal crayfish has indirectly more or less exterminated the native white-clawed crayfish, not by direct competition but by carrying a disease to which the native species has no immunity.
Surely enough aliens for anyone, but no, today I was at a conference in Brockenhurst organised by the New Forest Non-Native Plants Project, it was all about alien species, in this case mostly plants. It ranged across Crassula, giant hogweed, Japanese knotweed, Himalayan balsam, water primrose and several others. There was much discussion about control methods, although most species are here for good and it is just a matter of how we live with them. Most of these plants were deliberately introduced for our gardens and were often hailed as marvellous garden plants for many years before the problems started. Some plants do not seem to have caused a problem in themselves but the diseases they brought with them have, fungal diseases seem particularly to be a problem, sometimes skipping here to new species with deadly results.
So what have I gleaned from my encounter with the aliens? Well it seems we have been very slow to learn from past mistakes and increasing world traffic and trade will probably mean things will only get worse. Even though the spread of aliens species is regarded as second only to climate change as a threat to wildlife globally and costs something over 13 billion Euros a year in Europe, as a society we still don't really take it seriously. We are living in an experiment, we can do almost nothing to control it and we do not know what the outcome will be. What is certain is that with finite resources adding species is going to change things and some species will disappear or at least get much rarer, a lot of them natives. There will also be lots of unintended consequences, the introduction of grey squirrel was not intended to eliminate the red squirrel, it was supposed to give us an extra species. It is likely we will have a more uniform world, I will not need to travel to see some of the world's wildlife, it will come to me, but some of the wildlife unique to this area of the world might be eliminated or at least get so rare that I may never see it. For me encountering a species in the place it has evolved to be is part of the experience, the story of the place is encapsulated in the species.
Obviously for others this is not the case and every alien seems to have a champion or several. Many people willingly admit to spreading Himalayan balsam because they love it and think it improves the attractiveness of riverbanks. There are wels catfish enthusiasts that will go beyond the law to spread their favourite fish to new waters and lovers of the ruddy duck, Canada goose and grey squirrel who would never concede that their introduction was a bad idea. Then again I have a garden and am as much a sucker for the latest flash new plant as the next person, I wonder if any of the plants lurking in my borders are just biding their time before heading out across the countryside, I hope not but I really don't know and neither does anyone else.