Attritional conservation

Seas of Green – UPDATE

Last September we reported on the installation of black plastic sheeting on a couple of ponds in Bilsdale with the aim of shading out the non-native invasive plant species – New Zealand pigmyweed Crassula helmsii – which was accidentally flourishing there. The idea was to give the plant a taste of its own medicine by depriving it of light.

By two months the pigmyweed was becoming etiolated – pale and weakened due to the loss of sunlight – indicting the sheeting was effecting growth.

Crassula helmsii two months after black plastic sheeting applied. Copyright NYMNPA.

The sheeting was left on the two ponds through the winter and spring, and a second survey was carried out this July. The sheeting has killed off 100% of the pigmyweed that was covered, however pigmyweed plants remain around the edges of the ponds, where it was difficult to install the sheeting due to the surrounding vegetation and irregular shape of the pond edges.

One of the ponds covered by the black plastic sheeting July 2017. Copyright NYMNPA.

Contrast between the remaining Crassula helmsii at the edge of teh pond and under where the sheeting where the plant is now dead, July 2017. Copyright NYMNPA.The National Park Authority’s southern Apprentice Team will be spraying off the pigmyweed round the edge with a herbicide. The sheeting will remain on the ponds until at least late autumn to try to finish off this invasive species once and for all in this location, allowing the biodiversity of the ponds to recover.

Other non-native invasive plant species

New Zealand pigmyweed is one of the most common non-native invasive plant species found in England, along with Common rhododendron Rhododendron ponticum, Himalayan balsam Impatiens glandulifera, Japanese knotweed Fallopia japonica, and Giant hogweed Heracleum mantegazzianum. They were all introduced into the UK as garden plants. All of these species are present in the North York Moors to some extent, and work continues to control these particular plant species, without natural competition and predators, that can have such a detrimental effect on the area’s habitats and water quality.

We’re grant aiding the removal of rhododendron from important Plantation on Ancient Woodland Sties (PAWS), to help let in the light and give native ground flora a better chance of survival. Rhododendron can harbour the Phytopthora ramorum pathogen which is a great threat to forest species such as larch.

Himalayan balsam can be pulled out/cut down by hand but this needs to be done before the seeds are setting (August/September) because one shake of a plant can release 1000s of seeds that can travel up to seven metres potentially creating 1000s of new plants. Repeatedly removing the plants from a location before they can seed over a number of years will eventually mean this annual plant no longer regenerates there.

Japanese knotweed is trickier to tackle because it needs to be treated by careful herbicide injection. Repeated treatment can kill the rhizome which is so effective at spreading. The accidental breaking up of live rhizomes can spread the plant expediently. Careful disposal is vital.

We’re currently making best use of four years of funding from Yorkshire Water to tackle Himalayan balsam and Japanese knotweed along the banks of the Rivers Esk, Rye, Seph and Seven, through whole catchments and sub-catchments starting at the top. Both species are particularly menacing to river habitats as they out compete evergreen native species and die back in the winter leaving banks bare and prone to erosion increasing the sediment loads in the water.

Giant hogweed isn’t quite so common as the other plants in this area. It can be dangerous to deal with because its sap can burn skin so it needs to be treated with care. It can be cut down or tackled with herbicides, but like all non-native invasive species repeat control will be necessary to achieve eradication at a site.

There are lots of initiatives now across the country to address the threat of these out of place species, it can sometimes seem overwhelming but concerted repeated local efforts can have an effect.

Seas of Green

Simon Hirst – River Esk Project Officer

New Zealand pigmyweed (Crassula helmsii) was introduced to Britain from Tasmania in 1911. By 1927 it was being sold as an “oxygenating plant” for garden ponds and aquariums by Perry’s Hardy Plant Farm in Enfield. The first recorded occurrence of pigmyweed in the wild was at Greensted Pond in Essex in 1956. It spread widely and rapidly due to the increasing availability of the plant at garden centres and aquatic nurseries.

This non-native invasive plant is now listed under Schedule 9 of the Wildlife and Countryside Act 1981. It is an offence to plant or otherwise cause this species to grow in the wild. The plant is now also banned from sale in the UK, which is a significant environmental step forward.

Crassula helmsii - copyright NYMNPA.

Crassula helmsii grows around the damp margins of ponds and in water up to three metres deep. It starts as a small light green tussock on sediment. The tussocks grow and spread rapidly to form a dense mat of vegetation. Severe oxygen depletion can occur below dense growths. The dense mat out-competes all other aquatic vegetation, eliminates native flora and creates a poorer ecosystem for invertebrates and fish.  The plant grows throughout the year and has no dormant period. Thankfully the pigmyweed does not produce viable seed in the UK but it can re-grow from small stem fragments.

New Zealand pigmyweed is very hard to eradicate when it has become well established. The plant is tolerant of shade for long periods, tolerant of frost and dessication, and it cannot easily be tackled by any existing method of environmental control.

Recently New Zealand pigmyweed was discovered growing in two ponds in Bilsdale which are both adjacent to the River Seph. The river is one of our key wildlife corridors. Working with our Apprentice team, we came up with a plan to carry out a programme of control which will hopefully result in eradication of this invasive plant.

One of the ponds in Bilsdale covered in Crassula helmsii - copyright NYMNPA.

One of the ponds in Bilsdale covered in Crassula helmsii - copyright NYMNPA.

We’ve covered the ponds with black plastic sheeting in order to prevent sunlight reaching the pigmyweed. This will prevent the plant photosynthesising, and should eventually kill it. The unsightly but purposeful plastic sheeting will need to be left on top of the ponds for six months, and we will be reviewing the situation next Spring!

Depriving the Crassula helmsii of light - copyright NYMNPA.

Depriving the Crassula helmsii of light - copyright NYMNPA.

Temporary black plastic over the top of one of the ponds - copyright NYMNPA.

Patience and perserverance

We’ve launched a new concerted effort against two of the most threatening non-native invasive plant species in the North York Moors, bolstered by funding from Yorkshire Water over the next four years. We’re chasing down Himalayan balsam (Impatiens glandulifera) and Japanese knotweed (Fallopia japonica) in the River Esk and River Rye catchments.

As well as damaging existing ecosystems and decreasing diversity, both these species tend to overwhelm other plant species along river banks and the danger from this is that during the winter when these non-natives die back the banksides are left bare of vegetation so subject to erosion which increases the sediment getting into watercourses and smothering the water habitat.

Both plants are vigorous growers and virulent spreaders. Himalayan balsam disperses thousands of seeds per plant through exploding seed pods that can propel the seeds metres from the original plant. If the plants are next to watercourses the seeds can be carried downstream to colonise new areas. Japanese knotweed spreads through its underground rhizomes which are so effective that all remnants of the plants need to be carefully disposed of because even a small fragment of rhizome if given the chance to re-root will form a new plant.

The only way to have any real impact on the plants is to tackle them systematically starting at the top of catchments and moving downstream, and repeating the control year after year to remove any vestiges of the plants. This new funding will provide a much needed boost to efforts made over the last few years.

Himalayan balsam (Impatiens glandulifera) - it has a sickly, sweet smell, pink flowers and a bright green hollow stem. It can grow up to two meters tall. Copyright - NYMNPA.

Japanese knotweed grows to around three metres tall and has large alternate heart shaped leaves and a characteristic zigzag stem covered in purple speckles. Its flowers, which appear in late summer, consist of clusters of tiny creamy-white flowers. Copyright - NYMNPA.

We’ll be surveying the current extent of the plants and then resurveying each year to monitor the effects of the control. We’re using tried and tested control methods – hand pulling the Himalayan balsam before it gets the chance to seed and propogate, and treating individual Japanese knotweed plants with directly administered glyphosate injections to carry the chemical down into the rhizomes. We’ll be using contractors and volunteers to carry out the work coordinated by National Park staff.

Controlling and hopefully eradicating non-native invasive species in an area takes a long time. Simon, our River Esk Project Officer, is a real enthusiast for non-native invasive species control because he sees the detrimental effects the plants have on the river environment and on his beloved Freshwater pearl mussels. He can see the years of attrition starting to pay off as native vegetation starts to recolonise sites where invasive species have been removed.

“The secret of success is constancy to purpose” — Benjamin Disraeli

Along the riverbanks

John Beech – Land Management Adviser

A couple of weeks ago a demonstration event was held in Bilsdale, organised through the new (Yorkshire) Derwent Catchment Partnership*.

The event, kindly hosted by Mr and Mrs Lang, was held in order to share knowledge and experience when it comes to managing watercourses for wildlife benefits.

Demo Day 9 September 2015 - copyright NYMNPA

Initial discussions between landowners and Partnership organisations focused on  practical application. The Wild Trout Trust led on the practical demonstrations in the river. This included realigning some of the woody debris found in the channel in order to re-direct water flows. There was a lot of talk around the question of responsibility for trees in rivers, and when and where to remove or leave or realign them.

Demo Day 9 September 2015 - copyright NYMNPA

The practical demonstrations also included using natural materials to help stabilise banks in order to lessen erosion. One of the main issues with the Rivers Rye and Seph in Bilsdale is siltation which smothers river gravels and therefore inhibits spawning areas for fish with a knock on effect on fish populations. Riverside fencing and resulting buffer strips can have a significant effect in lessening agricultural run-off into a watercourse and so improve water quality. Creating 6 metre wide grass buffer strips along banks can not only help halt run off and help stabilise the banks with vegetation but also provide excellent habitat linkages adjacent to the river and so enhance connectivity along the river corridors running through a landscape.

Over this summer the National Park Authority has lead on another round of Himalayan balsam control, this time on behalf of the Partnership. This is the 8th year of this programme aimed at eradicating this particular invasive non-native plant at the top of the Rye catchment. Where the programme started, right at the top reaches of the the River Seph, the aim of eradication has almost been achieved, but repeat surveying and the pulling up of any individual plants that remain is vital to make sure this can be finally realised. Himalayan balsam can grow pretty much anywhere but it is particularly rife along watercourses where seeds are effectively spread downstream by the moving water. The main threat of the plant to a riparian habitat is that it tends to out compete native vegetation and then dies back in the winter leaving banks uncovered and subject to erosion.

Himalayan balsam (Impatiens glandulifera) - copyright NYMNPA

Enhancing the river for wildlife is a key goal for all members of the new Partnership. What is essential for delivery is the engagement of landowners and the identification of common objectives, and this kind of event can help with that.

*The Derwent Catchment Partnership includes the East Yorkshire Rivers Trust, Environment Agency, Forestry Commission, Natural England, Yorkshire Wildlife Trust, North Yorkshire County Council, East Riding of Yorkshire Council, City of York Council, Howardian Hills AONB, and the North York Moors National Park Authority.

 

Carry on saving the mussels

Simon Hirst – River Esk Project Officer

Our work to safeguard Yorkshire’s last remaining population of Freshwater pearl mussels has received a £300,000 grant from Biffa Award. The River Esk in the north of the National Park is the only river in Yorkshire which still has a Freshwater pearl mussel Margaritifera margaritifera population. The population is estimated to be approximately 1,000 individuals and is in drastic decline. Pollution and sediment build up, decline in fish populations and habitat degradation are all reasons for this.

River Esk Freshwater Pearl Mussel ~40 year old - NYMNPA

The grant received is part of a larger £1.5 million Biffa Award project (2015 – 2018) led by the Freshwater Biological Association that will also see river restoration carried out in river catchments in Cumbria and Devon where freshwater pearl mussels also survive.

One of the key elements of the project will be sharing knowledge and best practice with landowners, the local community and other conservation groups to help give the mussels a more sustainable future. The project will work with farmers to reduce sediment and nutrient input into the Esk, and volunteer groups and angling clubs will be involved in monitoring work such as sampling invertebrate life throughout the river and also restoration work such as planting trees along the river bank and tackling non-native invasive species. The funding will also help sponsor a Master of Research degree at Durham University, which will look at water quality throughout the catchment.

On top of this local effort, the national project will focus on improving the reproductive success of the Freshwater pearl mussel through the Freshwater Biological Association’s captive breeding programme. In 2007, mussels from the Esk were taken to an ‘ark’ facility in the Lake District which houses and breeds populations from threatened Freshwater pearl mussel rivers in England. We’re aiming for sections of the Esk to have been restored enough by 2018 to provide suitable habitat to accommodate the return of the juvenile mussels.

This is a brilliant opportunity for people from different backgrounds to get involved in the conservation of a rare and valuable species. They may not be cute and cuddly but freshwater pearl mussels are an important indicator species; if we get conditions right for them, it will have positive knock on benefits for a range of other wildlife such as otters, Atlantic salmon, dippers and kingfishers.

BiffaBiffa Award is a multi-million pound fund that helps to build communities and transform lives through awarding grants to community and environmental projects across the UK, as part of the Landfill Communities Fund. More information on the award is available at www.biffa-award.org.

Juvenile mussel at captive breeding facility - copyight Louise Lavictoire FBA

River Esk research work - NYMNPA

Encystement project - NYMNPA

This new project which started in March builds on the WREN funded three year Freshwater Pearl Mussel project which finished in February.  This project had similar aims to the new project – to educate and involve people, and to carry out restoration work to limit nutrient and silt input into watercourses which damages spawning gravels and juvenile mussel habitats.

WREN Project Outputs

WREN FWPM Project - river bank fencing - NYMNPAWREN FWPM Project - river bank fencing - NYMNPA WREN FWPM Project - river bank fencing - NYMNPA

 

 

WREN FWPM Project - bank stabilisation - NYMNPAWREN FWPM Project - crossing point - NYMNPAWREN FWPM Project - buffer strip - NYMNPA

 

 

 

 

WREN FWPM Project - tree planting - NYMNPAWREN FWPM Project - trough installation - NYMNPA WREN FWPM Project - tree planting - NYMNPA

 

WREN FWPM Project - river bank fencing - NYMNPAWREN FWPM Project - new cattle watering point - NYMNPA
WREN FWPM Project - gateway improvement - NYMNPA

 

 

WREN FWPM Project - Himalayn balsam control - River Esk Volunteers Task - NYMNPA

As well as nutrient and sediment free water the best habitat for Freshwater pearl mussels is a boulder stabilised substrate with pockets of coarse sand and gravel for burrowing. Water quality monitoring equipment was installed at the key potential re-introduction site on the Esk to measure a variety of water quality parameters such as dissolved oxygen, nitrogen and pH. Redox surveys were carried out to assess juvenile pearl mussel habitat quality – redox surveys measure the water quality within the river gravels (where the young mussels live). One of the Esk sites which was surveyed had redox readings which were potentially suitable for young mussels (which is really positive news), and a few other sites are very close to being suitable.

logoWREN is a not-for-profit business that helps benefit the lives of people who live close to landfill sites by awarding grants for community, biodiversity and heritage projects.

 

Potential FWPM re-introduction site on River Esk - NYMNPAThis is a long term effort. By 2018 all the work and funding over the last 10 years will hopefully come to fruition and the Freshwater pearl mussel will have a sustainable future in the River Esk.

Pink peril

Kirsty Brown – Conservation Project Assistant

Himalayan balsam (Impatiens glandulifera) - NYMNPA

Himalayan Balsam (Impatiens glandulifera) in the UK can be a contentious plant – some people like it and some people loathe it. From a water quality point of view, it’s bad news.

Now in the winter months the detrimental effects of the species are obvious on bare unvegetated river banks where the invasive plant has died back and where it suppressed other vegetation during the summer which could have stabalised the bank, and so the soil from the banks crumbles and slips into the water and chokes the river habitat.

Because of this, the National Park has been tackling Himalayan balsam in Bilsdale, in the west of the North York Moors, since 2008. It’s a long term task.

A targeted top-down approach is being taken which started with the River Seph in the north, with the objective of eliminating Himalayan balsam from the uppermost reaches of the catchment by repeat control over and over again, and expanding slowly downstream and onto the River Rye. It’s this targeted concerted effort that can make a difference as it is the abundant seed released each year and carried downstream that means the balsam is so prolific and recalcitrant.

Over the last seven years contractors, land managers, volunteers and apprentice teams have been tackling the plant. Hand-pulling and strimming have been the only methods of control used, due to the proximity to the watercourse. Permission from the land owners and land managers along the banks has been vital, and the local Bilsdale Beacon newsletter has been used regularly to keep the wider local community informed.

The work is proving effective – in 2014 only a few Himalayan balsam plants were found along the River Seph and were easily hand pulled by our apprentices, at the same time the banks are becoming revegetated with native meadowsweet and willowherb. This is very encouraging and makes the aim of the project to eradicate Himalayan balsam from the Seph catchment and the stretch of the Rye catchment that lies within the National Park, seem actually possible. The efforts over the past seven years have made great inroads into achieving this aim, but there is still work to do.

River Rye in Duncombe Park - where Himalayan balsam is being tackled through a Higher Level Stewardship agri-environment agreement

 

Not too late for water voles

Rona Charles – Senior Ecology Officer and Laura Winter – Aquatic Mammal Specialist and National Park Volunteer

There is often a gloomy tone to reports on Britain’s water vole (Arvicola amphibious) populations. For example, an Environment Agency spokesman has said that numbers in the UK are thought to have fallen by over 95% since the 1970s and a further 20% since 2011. But recent work by University of Aberdeen researchers shows that water voles can move from further from place to place than had been thought previously. This behaviour could give them a better chance to adapt to changing conditions, but only if there is still suitable habitat to act as corridors for them to travel through.

Despite difficult weather conditions over the last few years, and the presence of predatory mink, we believe that the North York Moors water voles are hanging on here in the uplands more successfully than in some other parts of the country. The best area here is in the east of the North York Moors, centred on Fylingdales Moor and Langdale Forest. The nature of this area means that the water voles are able to move and recolonize other sites when environmental and predation pressures render their usual habitats inhospitable. This is because

  • there is a large number of tributaries, ditches and headwaters connecting two river systems in the area;
  • there are large expanses of heather and forest providing cover for movement as well as pockets of water vole favoured habitat;
  • and importantly, the major landowners in the area, are sympathetic to the needs of the animal and try to manage their land accordingly.

Water voles need lightly-grazed wetland habitat extending beyond the immediate banks of slow flowing becks and rivers. Legal mink control can give the water vole a better chance of survival, although good wetland habitats provide better cover for the voles to escape the attentions of all potential predators.

We’re definitely not complacent though.

The habitat connectivity programme we’re rolling out in the North York Moors will help to reconnect fragmented areas of valuable habitat and should give the water vole more chance to safely relocate and hopefully spread out. Peatland restoration on a number of moors over the last few years, plus the ‘Slowing the Flow’ project above Pickering, is resulting in water being held back for longer on the higher ground and the run off during heavy rain slowed. This is an advantage for water voles (slower-flowing watercourses and less flash flooding of their burrows), as well as hopefully for people living further downstream.

More on the mussels

Gallery

This gallery contains 33 photos.

Simon Hirst – River Esk Project Officer As mentioned previously the River Esk in the north of the National Park contains Freshwater pearl mussels (Margaritifera margaritifera). It’s the only river in Yorkshire with the species which is internationally important and classed … Continue reading

More invasives

Alex Cripps – Conservation Graduate Trainee

As well as controlling Himalayan balsam along the River Rye and River Seph in the west of the North York Moors, the National Park Authority is continuing to tackle invasive plant species in the River Esk catchment in the north of the Park too. We concentrate our efforts along rivers and watercourses because this is where invasive plants are most problematic. Increased sedimentation in the Esk caused by invasive plant species is particularly threatening for the important protected species found there like the freshwater pearl mussel.

Himalayan balsam control work has been going well over the last few years in the upper Esk catchment so this year work effort has moved downstream and is now being concentrated in the Sleights and Ruswarp area near Whitby.

There has been a lot of help from landowners and members of the public letting us know where the balsam is growing. With a big concerted effort from our Mussel Volunteers and local contractors, coordinated by Simon Hirst our River Esk Project Officer, a huge amount of balsam has been pulled up this season. It is really important to hand pull or strim the balsam early, before the seed pods develop, as the seed pods explode catapulting hundreds of seeds up to 8m from the parent plant.

Seeds are transported by waterways and can stay viable in the soil for a few years, so it is going to be important to continue monitoring sites every year. It usually takes atleast 2 – 3 years to eradicate Himalayan balsam at a site. The plant can also be controlled by spraying it with pesticide (using a pesticide approved aquatic use when working near water) but this method is only used for areas with a dense coverage of balsam to ensure we’re not affecting other plant species.

Japanese knotweed is another non-native invasive plant found in the Esk catchment. Like Himalayan balsam it too creates large monocultures, shading out other plant species. Japanese knotweed does not produce seeds but instead it spreads vegetatively and can regrow from fragments of stems or rhizomes. It’s incredibly tenacious. So it cant be strimmed or mowed because that will just spread the plant and this makes it incredibly hard to eradicate.

The best method of control is by stem injection, whereby stems are injected with a pesticide. This is obviously very labour intensive but it is a very effective method and does not affect non-target plants. Spraying Japanese knotweed using a knapsack sprayer is also another method our contractors use, but this can only be done on a dry, calm day.

Hand pulling HB

Tackling invasives

Bill Shaw – Ecology and Conservation Land Management Adviser

In Britain, Himalayan balsam is a non-native invasive plant species. It is pretty and pink when it flowers, but it is a domineering plant that crowds out smaller native plants, and 1when it dies back in the winter it leaves sites with bare ground and no stabilising vegetation. This unstable bare ground along river banks where Himalayan balsam likes to grow is a particular problem because it leads to increased sedimentation in a river which detrimentally affects the river habitat.

Fortunately unlike other invasive plant species, Himalayan balsam is not too difficult to tackle and hopefully eradicate before it swamps a site. It can be pulled up in June/July, before it flowers and seeds. However it may take a few years of repeat pulling to actually get rid of the plant at a particular location.

For the sixth year in the row we’re tackling Himalayan balsam along the banks of the River Seph in the west of the National Park. We started at the top of the river catchment gradually edging down as well as going back up stream to repeat the control each year where necessary. The plan  is that we eventually eradicate the plant on this river.

It’s proving to be a resilient adversary but the amount of balsam now left on the Seph has been reduced enough for us to also move down onto the River Rye (which the Seph runs into). This season we’re commissioning control work, over a twelve week period, for a stretch of about five kilometres.

The vast majority of the control work will again be done by our three local contractors, who use a combination of strimming and hand pulling to remove this annual plant. Willing bands of National Park Volunteers will also tackle patches including in Duncombe Park National Nature Reserve. A survey conducted by our Volunteers in 2011 along the River Rye from the Seph confluence down to Helmsley has highlighted new areas where balsam is occurring so we know what we’re up against in our new drive against the plant.