Japanese Knotweed in Hemel: The Nickey Line Nightmare

Over the course of this blog I've covered invasive species problems from all over the world. Now I have come across a case much closer to home. Within a few miles, in fact, of the place I call my own, Hemel Hempstead, in South East England.

It gets called plenty, but I call it home...

Famous for giant oil explosions and recently being voted the UK's ugliest town, the latest travail it is encountering is the invasion of Japanese Knotweed on the rather nice Nickey Line pathway.

Japanese knotweed is native to Japan, Korea and China and was introduced to Britain in the 1850s (Bailey and Conolly, 2000). It is regarded as the most pernicious invasive weed in the British Isles (Mabey, 1996) and since 1981 it has been a criminal offence to introduce Japanese Knotweed (Hollingsworth and Bailey, 2000).Despite this, halting it's spread has proved impossible.

Distribution of Japanese Knotweed, then and now. Source: Cabi.org

It is an aggressive invader that causes substantial economic and environmental damage in the UK (Smith et al., 2007). Amongst these include impacts on native flora, increased flood risk, physical damage to buildings (its roots can grow through concrete) and it can obstruct public access to certain areas (ibid). The plant is problematic to remove as it spreads from its rhizomes rather than seeds (Environment Agency, 2013).
 

No place for a plant: Japanese Knotweed growing through a wall.

Luckily the local council is taking the required action in the very near future. Drains are to be replaced and improved, new tarmac will be layed on the path and the plants will be treated and removed.

In an attempt to ensure the hardy plant doesn't continue to grow or return, a large area around the plant will be excavated to a depth of about 3 metres. The dug up earth will be sent to a special landfill and a copper shield is to be inserted before the area is restored.

A site of Japanese Knotweed removal in nearby Watford, looks...rooty...?

If you happen to spot any possibly harmful plants in the Dacorum Council area, you can call the trees and woodlands department of the local council on 01442 228000.

Over and out

The Invader Inspector

Inspecting Invaders Christmas Edition!

Merry Christmas everyone! The day is now upon us so I feel much more comfortably saying it than I would if it was the start of November. That's right Tesco, it's not ok to have Christmas stuff on the shelves that early. For shame.

Anyway, rant over, you're probably here to read about invasive species. Today's piece is gonna full of seasonal cheer, but factual and sciency and stuff at the same time. A real Christmas cracker you could say!

To make the piece extra festive, I thought where better to rankle a case study from than Christmas Island itself! In my mind, it's permanently snow covered, the lamp posts are candy canes and everyone gets merry with Pierre Noel himself at the local on Friday night.

Merrrrry Christmas!!! First round of samichlaus is on him!

In reality, it's in the Indian Ocean. So probably not climatically suitable for permanent snow cover, but I hope they make the effort with the candy canes...

Location map of Christmas Island

In even starker reality, the island is suffering from an invasive species drama of Dickensian proportions. Playing the roles of synergistic villains, step forward Pulvinaria urbicola Cockerell (almost sounds like a name Dickens would come up with!) and yellow crazy ants.

Pu. urbicola is a honeydew producing scale insect and notoriously destructive invader (Gaigher et al., 2011). It has great reproduction potential and can become widespread on tropical islands And here's the Christmas crisis... it's been detected on Christmas Island (Neumann et al., 2014)! Oh no!

Pulvinaria urbicola, the scoundrel desecrating Christmas Island.

Introduction of Pu. urbicola to Christmas Island is likely anthropogenic; largely associated with movement of plant material to the island.

And the situation is bad. Christmas Island has experienced a large-scale ecosystem 'meltdown' (O'Dowd et al., 2003) as a result of interactions between scale insects, such as Pu. urbicola, and invasive yellow crazy ants.

Honeydew producing insects are a major problem. Not only do they themselves damage plants, they serve as mutualistic partners for invasive ants, exacerbating their impacts (Abbott and Green, 2007). Large populations of scale insects cause forest dieback, while increased honey dew levels facilitate the yellow crazy ants.

The ants themselves cause rapid, catastrophic shifts to tropical forests, affecting at least three trophic levels (O'Dowd et al., 2003). They extirpate red land crabs, the dominant omnivorous forest floor consumer, overwhelming them by their sheer numbers and bump them off by spraying formic acid into their eyes and mouths. The ants then occupy burrows and consume resident crabs. Starting to see where the 'crazy' bit of their name comes from...

The loss of crabs caused by this invader indirectly releases pressures on seedling recruitment and slows litter breakdown. The impact of which can be prettyyyyy big. 

Impacts of the yellow crazy ant (a) shows an univaded site, maintained by foraging red land crabs (b) shows a site 1-2 years after invasion.

In June and July of 2011, heavy infestations of Pu. Urbicola were discovered on Pisonia Grandis, a tree species on the south coast of the Island. 12 of 15 trees sampled had Pu. Urbicola presence, with 5-60% of leaves on each tree infested. And, of course, attracted by the honeydew they produce, yellow crazy ants were found nearby (Neumann et al., 2014).

Pisonia grandis forests are important to the island ecosystem, providing nesting and roosting habitats for sea birds and regulating understory vegetation. However, the tending of Pu. urbicola by invasive ants is implicated in the dieback and decline of Pisonia Grandis (Neumann et al., 2014). Climate change is also implicated in the forest decline, but there is strong evidence this is a secondary factor.

A Pisonia Grandis forest

At present there is no feasible chemical option for direct control of Pu. urbicola, and it is not significantly predated on Christmas Island (Neumann et al.,2014). However, biological control could be an option as introducing scale insect predators has aided suppression on oceanic islands (Smith et al., 2004).

So Christmas Island is facing a tricky situation, with three species seemingly intertwined in the threats faced by the Island's forest ecosystem. These interactions make the situation even harder to manage, but a biological control programme for Pu. urbicola on Christmas Island is underway.

I hope it proves to be successful, but am unsure of the effects that extirpating Pu. urbicola will have on the yellow crazy ant, which seems to be the greater issue... we can only wait and see what happens.

So that wasn't as festive as I'd hoped... I mean, a story about crabs being sprayed with acid and forests dying doesn't really embody the spirit of Christmas. I think that needs fixing...

Do you remember the piece I did earlier this year on the decline of red squirrels due to the invasive greys? Well those greys have now reached Santa Claus himself, and one cheeky little blighter has even stolen his hat! They really are causing havoc everywhere it seems!

The most heinous of crimes.

I hope he finds the delinquent squirrel soon, or he'll probably be very chilly when he's out delivering our presents. I know I'll be keeping my fingers crossed for the hats safe return.

Merry Christmas

The Invader Inspector

Invasive Species and Human Health - Imminent Illnesses in Europe?

In my previous two pieces on the impact of invasive species on agriculture, some examples of invader facilitated diseases cropped up (no pun intended...). This got me thinking, if invasive species can cause ailments to our farming activities, can they have direct negative effects on humans too?

I knew that mosquitoes cause diseases like malaria and dengue fever. I also knew that with changes in climate, their distributions are changing. So, I figured it was worth investigating further... with emphasis on Europe, so it has some 'closer to home' relevance.

Mozzies are vectors for a number of diseases including yellow fever, dengue fever, malaria and chikungunya (Akbari et al., 2013). Picking out dengue specifically, approximately 2.5 billion people worldwide are at risk, with approximately 25000 deaths a year (Guzman and Isturiz, 2010).

Aedes aegypti is the principal species facilitating Dengue spread (Halstead, 2008) and it's also responsible for outbreaks of chikungunya (Ligon, 2006). It is native to tropical Africa (Braks et al., 2004) but expanding in range, with Dengue occurrence closely following this expansion (Guzman et al., 2010).

A female Aedes aegypti, you don't want to encounter one...

In October 2012, Aedes aegypti was implicated in a large outbreak of Dengue fever in Madeira, Portugal (Sousa et al., 2012). By early 2013, more than 2000 cases had been reported (ECDC, 2013).

Notified dengue fever cases by week, Madeira, Portugal, 3 October - 25 November 2012. Source: Sousa et al., (2013)

So, maybe soon we'll need vaccinations before we go on holiday to some of Southern Europe? And I can't see 'Sun, Sea and Possible Chances of Deadly Diseases' catching on in travel brochures anytime soon...

Another concern is the Asian Tiger Mosquito, Aedes albopictus, an aggressive species with vectorial capacity for a number of nasty aforementioned diseases.

It is native to East Asia, but is expanding globally at a rapid rate, having colonised every continent bar Antarctica in the past 40 years (Bonizzoni et al., 2013). In the last 10 years the species has been the principal cause of Dengue and Chikungunya outbreaks in Hawaii, Central Africa, southern China and now, Europe too (Bonizzoni et al., 2013). Quite a spread, I'm sure you'd agree.

Aedes Albopictus: currently the most invasive vector species worldwide (Bonnizoni et al., 2013).

Focusing specifically on Europe again, the Tiger Mosquito was first recorded in Albania in 1979. It's now present in all Mediterranean countries and is moving north to countries including Belgium (Bonizzoni et al., 2013).

The Tiger Mosquito was the cause of the first notable invasive mosquito-borne disease outbreak in Europe. In the summer of 2007 in Ravenna, Italy, more than 200 cases of chikungunya were reported (Angelini et al., 2007). 

It's globetrotting nature presents a threat. Between 1990 - 2013, the number of people living in countries with Tiger Mosquito presence has increased from 3.2 - 5.1 billion.  The species is highly adaptable ecologically, can transmit many pathogens and is happy in both urban or rural locations. So, it's not just a globetrotter, it's also cosmopolitan. That could be an issue...

Global distribution of Aedes albopictus, now available in Western Europe! Source: Bonizzoni et al (2013).

Concerns over mosquitoes are rising as they have spread considerably since 1990 (Schaffner et al., 2013). Changes in weather patterns and land cover are known to impact vector borne disease transmission (Vanwembeke and Lambin, 2006). Climate change could also facilitate higher mosquito densities and spreads beyond current boundaries.

However, the principal driving forces for the spread of mosquito borne diseases have been anthropogenically driven, due to globalisation and inefficient public health measures (Schaffner et al., 2013). 

On the other hand, it is worth pointing out that other invasive mosquitoes such as Aedes Atropalpus and Aedes koreicus currently represent very low threats to European public health (Schaffner et al., 2013).

Aedes Atropalpus: not as much of a health concern.

Generally though, given these developments, mosquito surveillance is now essential to detect early invader presence and prepare for control of disease outbreaks (ECDC, 2012). Early eradications have been achieved for certain mozzies in France, Italy and the Netherlands (Schaffner et al., 2013).

Another invader I came across with the potential to inflict disease upon humans was Nyctereutes procyonoides, or, as we more commonly know it, the raccoon dog. Historically, it was restricted to the Far East, however, it now has a presence in much of northern and eastern Europe, with potential to expand further (Kauhala and Saeki, 2004).

The Raccoon Dog's native range (blue) and invaded areas (red).

The danger posed by raccoon dogs is their ability to transmit the potentially lethal viruses to humans, including rabies. In fact, as many as 55,000 humans are killed by rabies every year. The concern in Europe is that the racoon's flexible habitat use, high offspring numbers and large dispersal potential could lead to high population densities (Sutor et al., 2013).

Raccoon dogs, cute but be careful.

However, it should be pointed out that countries such as Finland and Germany have raccoon dog presence, but are also rabies free. And more generally, it seems the raccoon dog poses greater threats to wildlife than to humans in Europe. So I don't think we need to worry about large quantities of people foaming at the mouth anytime soon.

To conclude, there is ample evidence that we should be concerned about the impacts of invasive species with regard to human health, particularly concerning certain species of mosquitoes. The growing threat is entwined with global environmental change, anthropogenic and 'natural', as this is permitting the spread of the potential disease inflictors. Should we be concerned? I'd have to say yes, and if we're aware of the threat now, it should help mitigate the effects in the future.

Uninvadable Agriculture?: Cubes, Corn and Creepy Crawlies

Today's piece represents a unique situation for Inspecting Invaders. That's because I'm not going to talk about invasive species at all, well, except to make reference to a lack of them.

In my previous post, I painted a slightly worrying picture about how invasive species are reducing agricultural yields, and how this is set to become worse in the future.

However, during a recent reddit procrastination session, I stumbled across a link to this article on how it seems nothing can live in a corn field apart from corn. And it got me thinking, is this uninvadable agriculture?

The article discusses stories from two interesting books. The first is A World in One Cubic Foot, by David Liittschwager (a portrait photographer) and E.O Wilson (a Harvard biologist) (cool tag-team). David spent years travelling round the world, dropping one-cubic-foot metal frames into all sorts of environments, and the species he found were documented.

For example, in a Costa Rican tree, the aforementioned cube was found to contain more than 150 different plants and animals.

A cube hanging out in a Costa Rican tree top...

...and the species it was found to contain.

Countering this, scientific writer Craig Childs, tells the story of species surveys in a 600 acre Iowan cornfield in his new book, Apocalyptic Planet. The results bore a stark contrast to the Costa Rican tree census. This is because corn farmers really really value their corn. Anything which may eat, hunt or even bother it, is killed. The corn is also bred to fight pests. the ground is sprayed, with stalks sprayed again. Cause you can't be too careful.

A corn field. Plenty of corn not much of anything else.

In three days and two nights, he only came across one tiny ant, a minuscule mushroom, a single spider, a single red mite and some grasshoppers.

Yep, not much here apart from corn.

This is even more stark when considering that these prairies were once home to a rich variety of species. Now they're home to pretty much just one living thing.

Clearly this is good for food supply, but is it worth the loss of biodiversity? My opinion is that if the loss of biodiversity remains localised, species invasions are prevented, and sufficient corn yields are produced, then there is no issue with a farm taking precautions to ensure its productivity.

We need to be careful though with what we apply to our crops with regard to human health, as this blog post by Laura Tamjarv on an Argentinian atrocity demonstrates.

That's just my opinion, as the use of pesticides and such like is a delicate issue I'd be very interested to hear any thoughts anyone reading this may also have.

Over and out

The Invader Inspector

Invasive Species, Agitating Agriculture?

Well that management section was fun, I can barely remember what it's like to write about anything else. But the past is the past, I need to knuckle down and rattle through some more invasive species related capers. So, onwards we go!

When I was chatting with Hugo Watkins the other day about his farming blog, I flippantly asked him if he'd done a piece on the impact of invasive species on agriculture yet. That very second, the cogs in my brain slowly clicked into action.

An actual X-ray of the inside of my skull.

*Wait, I've just suggested something invasive species related...that means... Gah I know the answer to this one..*

...15 minutes later...

*That means I can write about it!*

And write about it I shall! Because it turns out, the impact of invaders on agriculture has been quite a big deal. AND it's likely to increase in future.

So, whereas Hugo's blog discusses how agriculture is contributing to environmental change, I'm looking at how environmental change is contributing to agriculture. Neat, huh?

Invasive species and agriculture, how costly could the impacts be?

Earth is now home to over 7 billion hungry humans, and we're heavily reliant on agriculture for food. However, invasive species can cause agricultural product losses worth more than a trillion US dollars per year (Oerke and Dehne, 2004). According to Ziska et al (2011), in their 'agronomics'  paper, ¹/₄ of U.S.A's gross agricultural product is lost to invasive species each year. Yipes.

For example. Asian soybean rust (Phakopsora pachyrzi), an invasive pathogen, has potential to inflict major soybean production damage in the U.S.. It is thought to have arrived from South America in 2004, having been carried by Hurricane Ivan. In future, with storminess expected to increase under climate change, its spread and negative agriculture effects could become worse (Ziska et al., 2011).

U.S states with confirmed detections of Asian soybean rust in 2006. Source: Economic Research Service

Invasive weeds can also pose agricultural problems. For example, Follak and Essl (2013) have documented the spread and agricultural impact of Sorghum halepense, an emerging invasive species in Central Europe.

The Central Asian native first arrived in Austria in 1871, was rare until 1970, but has expanded rapidly since 1990 and even more so since the new millennium. The S. halepense invasion puts approximately 41% of maize fields and 40% of oil pumpkin fields at risk of yield losses.

Cumulative records of S. halepense in Austria. Source: Follak and Essl (2013)

S. halepense can also act as a reservoir for Maize Dwarf Mosaic Virus (MDMV). Evidence for this comes from N. Italy, where S. halepense is widesprad and MDMV is commonly found on maize plants (Ivanovic et al., 1995), and Hungary, where yield losses from maize fields were reported to be up to 30.5% (Peti, 1983 cited in Ziska et al., 2011). 

Sorghum halepense, reducing Austrian agricultural yields since 1871.

The fast and ongoing spread of S. halepense is likely to increase under climate warming as more habitat becomes suitable.  In fact, all major agricultural areas in Austria and Germany expected to be climatically suitable by 2050 (Kleinbauer et al., 2010).

Additionally, management is troublesome, given that it has high seed production, high regeneration potential and is only sensitive to specific, high cost herbicides (Follak and Essl, 2013). Double yipes.

Invasive insects can also initiate farming frustrations. For example, African honey bees are moving north through America. These invaders readily capture feral and managed European honey bee colonies, with subsequent impacts on fruit production. Once again, this spread is likely to be facilitated further by climate warming (Ziska et al., 2011).

Current and projected range of Africanised honey bees. Black areas are where it is currently present. Grey areas represent the area that could support the bee if there are 120 days where the max temperature is >10°C

An even more serious insect invasion took place at the start of the 20th century when the introduction of the boll weevil (Anthonomus grandis) to the U.S. from Mexico resulted in almost the complete eradication of cotton crops in the U.S., with billions of dollars of crop damage (Ziska et al., 2011).

The risk to agriculture from invasive species is only likely to increase in future, not just due to rising temperatures, but also potentially from heightened winds and CO₂ increases. These factors could also interact. For example, the invasive weed, Kudzu, is known to respond strongly to CO₂ increases (Forseth and Innis, 2004) and is likely to move north as temperatures increase (Sasek and Strain, 1990).

Increasing CO₂ concentrations have been shown to increase the biomass of invasive kudzu.

The impacts of this on agriculture will be heightened by the fact that Kudzu can act as a host for Asian soybean rust, which I described above. Treble yipes.

This post has been a bit of a downer so far, so I should probably try and lighten the mood. Our food supply isn't completely doomed. We must also recognise the response of agroecosystems themselves to climate change. For example, rising CO2 could be used by breeders to improve existing cultivars. This could enable them to become more competitive against potential invaders and reduce productivity losses (Ziska et al., 2011).

To conclude, invasive species have been agitating agriculture for quite some time, and look likely to be an even greater annoyance as we move into the future. We should be aware of the impact invasive species can have on important ecosystem services, such as agriculture, and do our utmost to ensure that the future impacts of invaders are not as damaging as it looks like they could be.

Over and out

The Invader Inspector

Managing Invasive Species: Conclusion

Today marks the end for the 'Managing Invasive Species' chapter of this blog. I could keep going but no one likes a series that goes on for too long (Lost, I'm looking at you...). I'm taking the all good things must come to an end approach and retiring it at its peak.

Beginning with a recap, most conservation biologists believe that species invasions should be prevented wherever possible (Larson et al., 2013), however the methods for doing so are extremely wide ranging.

Aim for prevention where possible, things can escalate quickly once that threshold had passed. Source: Invasive Species Ireland

The first management approach I tackled was eradication. This was frequently effective in its initial aim of wiping out 'Invasive Species X' but often had negative side effects and could be expensive when taking account of environmental monitoring afterwards.

Second, I looked at legislation. In principle, this seemed to be a good idea. However, implementation of policy, especially at the international scale, was fraught with difficulty and often unable to become effective.

Next I looked at some alternatives. The strategy of human consumption (A fellow invasive species blogger has also recently analysed this strategy.) is thought to be potentially effective for Asian Carp management in the U.S.A. However at this early stage, it's difficult to be sure. Additionally this approach falls down by the fact that there are plenty of inedible invaders. 

I also considered biotic resistance, where we, as humans, don't act, and we allow natural predator-prey relations suppress the invaders. There was a case where this appeared to work, but it clearly isn't always effective, otherwise I guess there would be no prevailing invasive species! And this blog would be short on material...

Finally, I looked at public participation (for more on the related topic of 'Citizen Science' check out a recent post by Rachel Harris here). This approach has been effective at halting the spread of the Killer Shrimp in the UK, and it's cheap, but it is heavily reliant on the fact that people give a damn. And, maybe I'm bitter, but I don't think everyone does... And of course, there is plenty the public are plainly unable to do due to lack of resources.

So, all of these analysed. All with some good points, all with some bad. What is our best option?

In my opinion, when we uncover a potential troublemaker of an invasive species, we need to consider all the possible options for approaching its management. I mean, what would be the point in eradicating something when we can find a human use for it?

Research is clearly the key to choosing the best management approach for each individual case. Heck, it may even suggest a combination of approaches as the best way forward. I'm sure there are plenty of members of the public who would be up for removing invasive weeds rather than pumping in chemicals to eradicate them. 

Overall, here are some key point to take from this management series:

1. Where possible, the most effective course of action is, of course, to prevent invasive species establishing.
2. If dealing with an established invasive species, treat each case uniquely, and take the best possible action after considering all available evidence.
3. There is no 'one size fits all' solution to invasive species management. The benefits and costs of each approach should be accounted for in each case.

Invasive species management process cycle, note the high number of stages before implementation itself. Source Invasive Species International

When I started this series, I knew that I wouldn't find 'an answer' on how to manage invasive species, so to speak, but rather engage in a discussion of possible options to highlight the very fact that there isn't 'one'. There have been successes and failures when it comes to managing invasive species regarding all the strategies covered, but hopefully, as our ecological knowledge grows, the former will soon greatly outweigh the latter.

Over and out

The Invader Inspector