(Water) Plants under threat

The Guardian is highlighting today the threats to plants – and has used as it’s website picture one of Britain’s most threatened plants – Starfruit – a specialist of temporary ponds now restricted to a handful of sites as a result of habitat destruction, pollution and changes in land-use.

Starfruit used to be quite widespread on sandy acid soils, especially in the south-east.

The yellow square show where it used to live.

Now it’s hanging on by the skin of it’s teeth – in half a dozen ponds in the red squares – thanks particularly to the work of Plantlife.

But new pond creation also works for Starfruit: I even have a pond named after me which was created for the species on Stoke Common in Buckinghamshire!

You can see it here on Google Earth.

View Jeremy’s Pond, Stoke Common here.

The state of the Old Pond

The Old Pond today

My Old Pond is looking a bit overrun by Lemna so it’s with some relief that in a recent dip I found practically the same range of animals as this time last year; there were a few late staying tadpoles too.

The biggest difference between now and autumn 2009 is fewer Pond Olive mayfly larvae, and as far as I can see no Whirlpool Ram’s-horns – which is interesting because there were a lot last year. Maybe they were affected by the summer draw-down – it’s true that you don’t see Whirlpool Ram’s-horns in temporary ponds. I also wonder whether the abundance of duckweed has affected these two species.

There are many fewer Pond Olives this autumn - I think they rather like new bare ponds and are no so common where vegetation is abundant

Overall, the total number of species is down slightly from 23 to 19 – not that much of a difference really. And our Big Pond Dip score – which is based on the big groups present (dragonflies, bugs, beetles, caddis and so on) – is virtually unchanged: 47 instead of 52 (the difference is due to no water bugs).

There are still three dragonfly species, including lots of Large Red Damsel larvae, plenty of my favourite little pond snails the Smooth Ram’s-horn, and a good range of water beetles – with a dozen species they make up most of the variety of species though being in low numbers they’re not very conspicuous – you have to look around for them. One interesting arrival is a little water beetle that loves more leafy and overgrown conditions called Hydroporus memnonius – its one of the Little Brown Jobs of the pond world: a pretty little chestnut brown creature. There’s a couple of other water beetles that weren’t there last year as well.

I’ve still got caddis which is important because they’re one of the groups which should be present in natural unpolluted ponds: and I’m hoping to see more hatch and grow overwinter.

So I’m now waiting with interest to see what will happen to the duckweed this winter: will the String Moss provide some competition for it? Or do I now have a permanently duckweedy pond? And, most important of all, what difference does it make in the long run?

Breaking news: the Lawton review

(Professor Sir) John Lawton’s review of England’s Wildlife Sites and Ecological Network is out.

It’s pretty policy-wonkish stuff, as is necessary for this kind of report: so not exactly a bed-time read except for the most seriously sleepless (it’ll be my homework for the weekend).

But good to see ponds getting attention. A couple of snippets:

“Ponds are important habitats for a wide diversity of wildlife and can provide ‘stepping stones’ for many species that use freshwater habitats to move across the landscape (Webb et al. 2010; Williams et al. 2010). An estimated 70% of ponds were lost from England since 1880, with much of the loss occurring in the second half of the 20th century as a result of agricultural change and urbanisation (BRIG 2007). Since 1990, however, this trend has been reversed, and the latest estimates reveal an increase in the number of ponds of 1.4% per annum between 1998 and 2007 across Great Britain (Williams et al. 2010). In contrast to the recent increases in numbers there has, however, been an apparent decline in pond quality. In 2007, 80% of ponds were assessed as being of ‘very poor’ or ‘poor quality’, a 17% increase in the proportion of ponds in these categories since 1996 (Williams et al. 2010).”

And:

‘More healthy ponds (Section 4.3.4), for example, mean a lot more wildlife (Halliday 2010).‘

Obviously these chaps are pretty sound when it comes to ponds!

Incidentally, the Williams of Williams et al is Penny Williams, Pond Conservation’s Technical Director.

Is the eel becoming a thing of the past?

Well, perhaps not if the Association of Rivers Trusts has anything to do with it, and as reported in the Independent today:

http://www.independent.co.uk/environment/nature/bypasses-seal-deal-for-eels-to-return-to-britain-2087030.html

One thing its worth remembering is that eels don’t just live in rivers: they are found in all kinds of freshwaters, including ponds.

Indeed making high quality ponds for them – which we are doing – could be an important part of the conservation story – not least because so many existing ponds are in a terrible state.

Is the Salmon becoming a thing of the past?

Salmon eggs

I like ponds but I also love rivers so I was interested in this snippet from the south west of England on one of those slightly obscure websites where important environmental data are published but probably rarely read.

This one is about Salmon in the south-west of England. They say:

‘Salmon are a good indicator of the overall health of the freshwater environment‘.

They continue:

‘Salmon populations have declined in most rivers in the region, however this varies in each river catchment and with the weather patterns each year.  There was a slight improvement in numbers of returning fish and spawners in 2000 and 2001 and again in 2004, but the general trend has been downward since the late 1980s and the numbers in 2009 are estimated to be the lowest in the time series.’

Aside from the pedants point that the Salmon is obviously not an indicator of the condition of the whole freshwater environment – you don’t find them in ponds and small lakes that aren’t connected to the river network, so they can’t tell us about the condition of these habitat – aside from that, this is worrying stuff.

And it’s not just in the south-west this is happening either – see here.

I can’t help wondering how this squares with the Environment Agency’s recent report that there are ‘Record numbers of salmon and sea trout in iconic English rivers‘ – presumably they were just referring to iconic rivers, not all of them!

Random misinformation

With a bit of time to spare on a Sunday night I thought I’d spend a few minutes doing a bit of ‘myth swatting’: stuff people write on apparently reputable websites that doesn’t really stack up in the real world.

So here we are with a random selection of pondy misinformation:

‘Dragonflies need marginal plants when their aquatic larvae emerge as adults from the water‘. Not really true: there are plenty of dragonflies and damselflies that will emerge on low growing grasses, including particularly the species that are common in garden ponds like Large Red Damselfly, Common Darter and Broad-bodied Chaser. And of course these are often the same species that are quite happy to walk some distance from the pond, and even head into the bushes, to find an emergence site.

‘Tap water may be used to fill a pond (the chlorine will quickly disappear)…….‘. Tap water is usually a bad idea because of excessive nutrients, and most water is no longer simply disinfected with chlorine but with a mixture of chlorine and ammonia called chloramines – and these do not evaporate from the water.

‘Summer is the time for pond dipping…..‘ – Of course you can go pond dipping any time but if there’s one time that is best, it’s spring from about March to May when the greatest variety of animals is still in the pond before they have all emerged as adults. Obvious once you’ve looked in a few ponds.

‘….and maintenance/disturbance should be kept to a minimum as many species are breeding (in summer, that is).’ I’ve never really fathomed why things living in ponds would be especially sensitive in the summer. And of course quite a few of them are not in the pond in summer.

‘The most important task in autumn is to keep the water free from decaying vegetation.’ Decaying vegetation is a tricky issue – ponds that are typical garden-pond shaped (i.e. rather too deep for their area) seem to have a tendency to become stacked to the gunwales with dead leaves, which almost inevitably leads to very low oxygen levels. These ponds usually have very limited animal communities (though they may still have breeding Common Frogs and Smooth Newts). But in broad and shallow ponds, which should be better oxygenated, moderate amounts of leaves, twigs and decaying organic matter are perfectly natural, and provide food and shelter for a variety of creatures. In these ponds it’s possible that there will be enough oxygen and biological activity to stop rapid build up of leaf material – though a good long set of observations is still needed to confirm this.

‘Remove dead and dying foliage regularly and prune back excess growth of submerged plants.’ Over-tidying probably doesn’t do any good for wildlife – it certainly doesn’t happen in nature. And removing submerged plants is likely to be a big mistake – it takes away habitat from otherwise rather barren open water, and leaves the stage free for algae to take over.

‘Place netting over the pond where practicable as this can help autumn maintenance by keeping leaves and debris from falling in and fouling the water‘. Well, this is only really a problem if you’ve got a pond with a deep – 50 cm – sump. Just possibly a net might be worth it then. But in shallow, well-oxygenated ponds, falling leaves and twigs should be beneficial rather than a problem.

How to make a really good wildlife pond: an update

In April 2009 I made some suggestions about how to make a good wildlife pond:

- Clean water

- Plenty of shallows

- Focus on the edges: they’re the place where most things live.

Since then, looking at the ponds in my garden and at ponds in Abingdon more widely, I’d add a couple of further observations.

It looks like one of the hardest things to get right is the water plants. It’s not easy to get a variety of native aquatics growing in new garden ponds – which is perhaps why retailers have focused so much on selling us non-natives like Curly Waterweed (Lagarosiphon major, often called ‘Elodea crispa’) which seem to take quickly and easily more or less wherever they are put.

In fact, in most of the garden ponds I’ve looked at there have been hardly any native water plants – with the exception of duckweeds. Unlike the animals, the water plants really are a bit of a disaster area in most gardens.

Our detailed surveys of Abingdon garden ponds also confirm that the best ponds do indeed have the cleanest water. But there are sometimes exceptions: some low conductivity – pretty clean – ponds have poor wildlife communities – look at the bottom left of the graph below.

The graph shows how as conductivity increases (usually a sign of increased pollution) the number of animal species found in the pond goes down. There is an interesting apparent exception.

In the Abingdon survey there was also another pond which, at first sight, appeared to be an exception to the general rule. This pond – on the upper right of the graph (with a circle around it) had a high conductivity and a high number of species.

But this pond is actually a reminder of the limitations of conductivity as a measure of pollution: conductivity is a cheap, quick and accurate way of measuring the total amount of chemicals dissolved in the water, both those present naturally and those added as a result of human activity. It’s often high where water is polluted, so can give us clues about the presence of pollutants but it doesn’t tell us exactly what is dissolved in the water.

In this case, despite the high conductivity, more detailed measurements of the pond water chemistry showed that this pond had pretty good water quality with near-natural nutrient levels. In this case the high conductivity was caused by there being more calcium in the water than in most other ponds in Abingdon.

Added to that the pond had a completely natural base – being dug into wet peaty soil with no liner – so had better margins than most other ponds. It was also the second largest pond in the survey.

So although it appears to contradict the general trend at first, actually it fits the predictions pretty well.

It really does seem to be important to have clean water.

Oxygen in my garden ponds: 15th September update

Oxygen in the my garden ponds: date and time along the bottom (each vertical line shows midnight) and oxygen level up the side, in milligrammes of oxygen in each litre of water. Click the graph to see a larger picture.

I haven’t measured the oxygen for a few days – so I thought it was time to make another set of measurements.

Interestingly results are staying pretty consistent: the open-to-the-full-sun New Pond has the highest values; Katy’s pond – the shallowest, most shaded and with plenty of mosses – is intermediate.

And the Old Pond – also shaded for most of the day but also covered in Lemna, is the lowest.

However, it’s worth noting that although it seems pretty clear that the Lemna is reducing the amount of oxygen in the Old Pond, its still well above the very low oxygen levels we saw a few days in a very leafy and rather deep pond at Sparsholt College.

What’s far from clear at the moment is what effect these differences are having. That’s a question which will be harder to answer.

Bat pond

A rare site (and sight): a pond thick with underwater plants

Here’s a sight that’s sadly rare in southern England: a beautiful pond, protected from pollution by its woodland location, with crystal clear water and water plants growing throughout – just as they are meant to, but these days, because of water pollution, so rarely are.

But for me – a mostly daylight creature – the exiting bit was the bats.

Because I was at this pond, which is just 5 miles from the centre of Oxford, with local bat lovers who come here because ponds are a magnet for bats.

In this case there were water-loving Daubenton’s bats feeding over the pond and Brown Long-eared and Natter’s Bats nearby – quite a few of our bats are attracted to water because it’s a good place to feed.

This pond is definitely a Priority Pond: as well as the bats it also has Great Crested Newts – luckily it’s in a location where it’s future is as assured as is practically possible.

Jon’s post on frogs in the countryside

Just in case you didn’t read this in the comments, I thought it would be of general interest.

So, over to Jon…

The problem is that there is no real data on common frogs in countryside ponds. Frogs are recorded as present in garden ponds – but a more useful measure would be peak spawn counts – giving a relative idea of the breeding population.

The NARRS survey [National Amphibian and Reptile Recording Scheme] revealed 50% of the 400 ponds surveyed had frogs. Urban garden pond surveys in Essex – for example in Rochford, Southend, Uttlesford and Brentwood – revealed upwards of 80% of ponds having frogs – but again this is just presence and there is no information on relative population status (spawn clump counts).

An interesting statistic was the low numbers of great crested newts in ponds – lower than 17%, and in some cases as low as 8% – interesting comments from the wildlife trust about this ‘common’ species actually being rare in garden ponds (which tend to be unsuitable for cresties).

I suspect that the opposite is true of the common frog: it is assumed to be common in the wider countryside on a local scale when it is in fact declining or being lost altogether.

There are some large populations of frogs in semi natural ponds in Essex – when I say large people probably would think about thousands of frogs

I recorded around 300 clumps of spawn in three water bodies – two reasonable sized ponds and in the wheel rutts of motorbikes in a flooded meadow – the majority of the spawn was in the shallow water of the wheel ruts with a much smaller number in the two deeper ponds – the reason possibly the presence of newts – avid predators of tadpoles!

This is from experience in the East of England. I am not sure whether there is any count data in the NBN dataset – so it would be good for the Big Pond Dip to record the peak numbers of frogs found in ponds during the late winter and spring so this can be compared to any count data from the NARRS survey.

I am looking forward to the frogs finding my new garden pond next spring as I believe that it is designed to be suitable for frogs to breed successfully – a temporary shallow warm pond.

I went out tonight to look at the pond and I have now got two water beetles in the pond!