Rich Pickings For Dinosaur Diggers

Good news this week for any of our listeners who are budding palaeontologists - there are still plenty of dinosaurs out there to discover. That's according to a new study by Steve Wang, a statistician at Swathmore College, Pennsylvania and Peter Dodson, a palaeontologist at the University of Pennsylvania in the US. They looked at the number of skeletons found so far from each known dinosaur genus (that's one group bigger than species - so humans are homo sapiens which means we belong to the homo genus and sapiens species). They plugging those numbers into an established mathematical model which links the fossil sightings to the likely number of unseen dinosaurs and they predicted that there could have been a total of about 18 hundred and 50 genera of dinosaurs in the world, of which we have so far only found 527, so there should be plenty more out there. But we will never find every last dinosaurs because not all of them will have left fossils behind and the diversity of dinosaurs that we have found is biased by the availability of fossiliferrous rock outcrops. but, the good news is that around about 90% of the dinosaurs which are discoverable will probably be found within the next 100 to 140 years. So if you're hoping to discover something fiercer than a T-Rex or bigger than a giganotosaurus then it's definitely still worth getting out there to have a good look.

9th Sep 2006

Fish Populations Out of Their Depth

Nearly half of the fish that we eat today haven't been caught from seas, rivers or lakes of the world but began life in a farm just like the beef, pork and chicken that we eat. That's according to the latest report from the UN Food and Agriculture Organisation, the FAO. There has been a massive boom in the amount of fish that are farmed, a process known as aquaculture - in 2004 we were growing 45 million tonnes of fish compared to 60 million tonnes which were being taken from the wild. With the number of people in the world climbing ever higher, there will be more and more demand for fish to eat, but the problem is that we are already maxing out the amount of fish we can catch from the sea - even with more fishing boats with bigger and better fishing gear we are still catching about the same about of fish from the seas that we have for the last few decades. So, maybe the only way we're really going to be able to meet this increasing demand for fish is to grow them ourselves. This week at the BA Festival of Science in Norwich I went to a session all about "Should we eat fish" - and it's unclear whether this increase in farmed fish is a good or a bad thing for the world. On the negative side, there worries that farmed fish had spread diseases and parasites to wild fish, and that escapees from fish farms which can genetically contaminate the local wild gene pool. And some farms can generate lots of water pollution from leftover feed and excrement from the fish. And then there's a problem that many of the farmed fish are fed on other fish, which are still being caught from the seas. But, on the positive side, farmed fish does help to feed people in the developing world and could provide a very important, more secure source of food. And there are some species that are becoming endangered in our seas that maybe we can grow and so leave alone the wild stocks. Did you know that cod, that favourite ingredient for fish and chips and fish fingers, are now being sustainably grown for the first time in the Shetland Islands. It's early days, but if it takes off, this could help reduce pressure on those wild stocks - maybe one day the Japanese will be farming blue finned tuna for their sushi.

9th Sep 2006

Science Update - Mercury Pollution and Public Transport

Bob - This week the topic is climate change, where all the news seems to be bad. And in fact I'll bring you some bad news later about how climate change may be leading to an influx of mercury in the environment. But first, some good news. We all know that taking public transportation over driving is the right thing to do as far as the environment is concerned. But new research suggests that, in some cases, what's good for the environment may also be good for you.

Chelsea - It's an old debate that's been rehashed countless times: Train commuters claim that their ride is less stressful because they don't deal with traffic; drivers swear they're more relaxed because they're in control. Now new research on New York commuters supports the train riders' side. Environmental psychologist Richard Wener of Polytechnic University in New York and his colleagues asked commuters about their psychological states before and after commutes.

Richard - And what we found was that train commuting was significantly less stressful than car commuting, that it seemed to be largely because it was perceived to be significantly less effortful and also more predictable.

Chelsea - Wener says this predictability is key, because it means people can relax knowing they'll get to work and back home on time. Of course that requires that the commuter trains run more or less on schedule, something that's not true in every city. He adds that the effects of stress are not only psychological but also physical, and the daily commute is a potentially significant but still poorly understood contributor to people's stress levels.

Bob - Thanks, Chelsea. Wildfires raging at unprecedented intensities in the north may be unleashing massive amounts of mercury into the environment. The mercury has accumulated harmlessly over thousands of years in the soils of wetlands, particularly in a type of soil called peat in northern North America. But Michigan State University ecologist Merritt Tueretsky says that in just a few decades, forest fires in these regions have more than doubled in size-a result of global climate change.

Merritt - Forest fires don't just burn forests. And our data show that when peat layers within boreal wetlands burn, it releases very large quantities of mercury into the atmosphere.

Bob - She says the mercury could disperse over long distances and find its way into the food chain, where it could eventually reach animals and people.

Chelsea - Thanks, Bob. That's all for this week. Next week we'll bring you a piano piece composed by Mount Etna. Until then, I'm Chelsea Wald.

Bob - And I'm Bob Hirshon, for AAAS, The Science Society.

September 2006

How Flowers Are Turning Up The Heat

Chris - Here's Beverley Glover from Cambridge University who works on plants and has also found out how they're using jiggery pokery to attract pollinating insects. What's your work about and how is this all achieved?

Beverley - What we're interested in are the adaptations flowers have that make them particularly attractive to pollinators. If you think about a flower, the petals - the bright shiny bit that you like to look at - is really there for only one reason: to attract animals. Different plants have come up with different ways of making those attractive to animals. The one we've been working on most recently is miniature lenses on the petal cells that warm it up a few degrees. We've been doing some work with bumble bees in labs and in flight arenas to test whether they prefer warmer flowers and whether that would be an advantage if the flower could attract more pollinators in the wild.

Chris - And does it work?

Beverley - It seems to work. Having those lens-shaped cells makes the flower warmer and the effect is strongest at dawn and at dusk and we know that bumble bees need extra help at dawn and dusk when it's hard for them to get that big fat body off the ground to fly. So what we've been doing is giving them artificial flowers of different temperatures and seeing whether they prefer the warmer ones and whether they can learn which colours of flowers might be warmer than other colours. It seems as though they can. They can work out that some colours are warmer than others.

Chris - Because the dark colours absorb more energy?

Beverley - Well that would be one way of doing it and it certainly seems that in the wild, from our very early preliminary work, dark coloured flowers are generally warmer than light coloured flowers.

Chris - So why are they all dark then?

Beverley - Because there are all sorts of other ways of doing it and it's not just about warmth. A pollinating animal is interested in being able to spot the flower easily from a distance so it needs visual contrast to the green of the leaves. It also needs to be able to work out where to get into the flower at a short distance, and so there are short distance visual effects. And there's beginning to be some data from work of ours as well about them liking the feel of different flowers, so tactile effects might have a role too. So temperature is just one part of the bag of tricks if you like.

Chris - But why do they like it when it's warmer? Why should that be more attractive?

Beverley - For a bumblebee we think it's about metabolic reward. They need the sugar from the flower to make energy to fly but they, like you on a cold day, might get more energy more quickly from a warm drink than a cold drink. It saves them from using their own energy to warm that nectar up if the flower's already providing it at a warmer temperature.

Helen - And with the bumblebees it's all about being cold blooded. They're not like us mammals; they rely much more on their surroundings to get themselves warm and active for the day's activity.

Beverley - Yes that's right. There's a lot of evidence out there that many insects will back in warm flowers just to get the heat. What we've done that's different is just to show that just warming the flower up by a couple of degrees, just warming the nectar up to give a warmer drink, makes the difference as well. It's not just about sun bathing; it's about getting a warm drink as well.

Chris - How far back in evolutionary terms do you think this goes or is that a very difficult question to answer because there's not a fossil record for plants quite as well as there is for other things?

Beverley - You'd be surprised how good the fossil record for flowers actually is. But it's a difficult question to answer because there's probably a whole range of different ways of warming a flower up and some of them won't fossilise, so for instance tracking the sun. This is not something you'd pick up from a fossil and there are certain plants that do that. The cells we've been looking at, the little lens-shaped ones that warm the flower up, we know that around 80% of flowering plants have those including if not the oldest flowering plant family that's still alive today. Probably the second or third oldest groups have those cells, which suggests that it could have evolved quite early.

Chris - Because insects have been around for quite a few million years. So does that mean that plants have been up to this trick ever since then?

Beverley - It's an interesting question. There's a lot of debate out there as to whether the flowering plants, which are very very rich in species number compared to non-flowering plants, actually underwent that radiation into so many species because the insects were also radiating into so many species at the same time. In the fossil record there are a lot of flowering plants appearing as some of the insect groups expand, so it's possible that that link has been there for quite a long time but it's difficult to prove.

September 2006

Predicting The Weather

Helen - So we want to know: how can we predict the weather? What's this all about? How do we know that it's going to be 19 degrees in three day's time? Where do we start off with that sort of thing?

John - It's a good question. Weather prediction is a bit like putting together a big jigsaw puzzle: you get all the pieces and you just have to assemble them all in the right way. A lot of modern meteorology is derived from computer-based models which take into account all sorts of equations and parameters and put them together to make an output. But what we use here is an awful lot of bench meteorology and looking at basic fundamental physics and working out how that affects our temperatures. So by looking at the thickness of a set level of the atmosphere, we can say that a thicker part of the atmosphere would be warmer and as we see how that tracks across the country, that will have a bearing on the temperature as well.

Helen - And how soon can we predict the weather and the temperature? Can we talk about it in half an hour's time in a particular location or and hour's time or do you have to work in longer blocks of time than that?

John - With forecasting it tends to be that the sooner and shorter-term forecasts tend to be more accurate. As you go further out into the future things tend to be a little bit more variable.

Helen - So I'm better off finding out what's happening in thirty minutes than I am the end of next week. But another thing that people in England are especially keen to know is when is it going to rain? How do we go about predicting whether it's going to rain or not?

John - A good thing to do is to look at the bigger picture. Looking close to home you can't really see much. So if you look at where the weather is going to come from, that gives a better indication of what the weather has in store. So we look at things like satellite pictures to work out how the weather is developing above the Atlantic, for example, and can see how that moves across us during the week. For example, we have a tropical storm developing out in the Atlantic at the moment, which is due to come across Bermuda later this week. That is going to produce a lot of moisture and a lot of warm air that is eventually going to come across us here in England. So that's going to have a huge influence on the weather we get.

Helen - So you're basically saying that it's going to rain next week.

John - It will start raining, but we'll see.

Helen - So essentially it's all about looking at what's upstream of us and working out which way it's coming in. Is that sort of the key really?

John - That's exactly it. It's about looking at where the weather comes from and the air masses that we have. Each of them is from a different source. For example, air that comes down from the south west tends to be very moist and very warm, whereas air that's coming in off the continent is very dry. So when continental air comes across us in the summer, it tends to be very warm. But in the winter time, it's cold air and can be generally a very chilly period especially for us over in the eastern parts of England.

Helen - Do you have an excuse for when the weather forecast isn't quite right? Or are we asking far too much of you to get it perfectly right all the time?

John - I think the best thing to do is to look at why it went wrong. There's always a reason for why things didn't quite go to plan, so if you can work out why it didn't go right first of all, you can make it better next time. There are a lot of things that could potentially go awry so it's just about keeping your eye on things and keeping up to date with the latest weather.

Helen - Finally, what's the deal with the Gulf Stream with talk about climate change and so on? Is it really true that temperatures could go down now instead of up in this warming world of ours?

John - It's true that that Gulf Stream is a very important factor in our weather here. For our latitude we're about nine degrees warmer on average in this north western corner of Europe. It feeds a lot of warm water up from the Atlantic and if that were to change it would definitely have an effect on our weather here. However, it would probably be evened up with other things going on with climate change, so at the moment it's very difficult to see how much of an effect it would have.

September 2006

Climate Change And Migrating Birds

Chris - Right now we're going to talk to Marcel Visser who's at the Netherlands Institute of Ecology. He's going to talk to us about how climate change is having a fairly major impact on animals that migrate and how they then reproduce. Tell us about your research and how you went about studying this problem.

Marcel - Well we have studied migratory birds in the Netherlands for a long time and one thing we noticed at one point is that the birds are coming in earlier. They were also laying earlier. The pied flycatcher, which comes over from Africa, seemed to be laying its eggs very quickly. In the old days it used to be two to three weeks between arrival and laying, and now it is only a week.

Chris - So birds are leaving Africa, they're leaving according to when they think it's the right time to come back, they're arriving but they're arriving at a time when the seasons have already moved on.

Marcel - Yes, it's very difficult for the birds to predict the conditions when they are all the way over in Africa. The birds use some cue like day length or an internal clock and it used to work very well. But now, by the time they come back, spring has already advanced there quite a bit and it's too late to really take advantage of all the food that's around. There's only a very short period where food is around in the forest, and this is quite important to realise. There's only about two or three weeks where there are a lot of caterpillars around to feed the chicks.

Chris - So how badly are the birds being affected and is this something we can actually do something about?

Marcel - Well in the case of the pied flycatcher we know that the majority of the birds now have their nestlings in the nest too late. We know that by the time they start feeding the nestlings caterpillars, the caterpillars are already on the decline. The other things we have shown is that there are different areas within the Netherlands and some of these areas have a very early food peak, the birds breed early, the caterpillars breed early and everything is early. In other areas, especially where there is poor soil, the peak is a bit later. It is clear that the pied flycatchers in these early areas are really too late, and you can see here that they are declining. The numbers are dropping and in some of these areas the flycatchers have completely disappeared. In the other areas, the poor areas, where food is late, they just arrive on time to raise their offspring and they're just about hanging on. So they're not declining there. It's a very clear effect on population numbers.

Chris - Do you think that this is going to be confined to this species of bird or are other migratory birds other than pied flycatchers likely to be affected?

Marcel - I think it's a very general pattern, especially for the long distance migrants and the ones that come from Africa because they have no idea how things are changing here. The solution, if you ask me what we can do about it, is to reduce the increase in temperatures. That's the only thing we can do.

Chris - It's not really a short term solution though. This is a couple of hundred years of carbon dioxide pollution and if we try and stop it now, it might not be in a do-able amount of time.

Marcel - If we now reduce our CO2 output by 60% and the increase in temperature will still be two degrees in the next 100 years, that is something we can't do anything about. But if we keep going on like we do now, it will be nine degrees, and that's not a trivial difference for the birds. What will happen with these pied flycatchers is that we will see natural selection. The birds that arrive early will get most offspring and these offspring will also arrive earlier as we know that this is heritable. So there is some scope for adaptation in the birds, but the rate of adaptation will be slow. So if we can keep the increase in temperature at a reasonable level, the birds will probably be able to follow that. But if we carry on the way we are going, then the increase in temperature will be so rapid that there is no way that the birds can keep up.

Chris - So are these birds able to adapt to climate change?

Marcel - Well that's actually the thing we're looking at in close detail now. We're looking at the kind of selection there is and the kind of heritability there is. What we can estimate now is that they will be able to evolve in time but it critically depends on how fast the climate is going to change. It's down to the rate of evolution in these birds and the rate that we impose on them.

September 2006

A New Source of Atmospheric Methane

Helen - Well let's stick with changing climate and the changing world around us. As the world warms the permafrost is beginning to melt, which is allowing bacteria to change carbon-rich material laid down over 30 000 years ago into the greenhouse gas methane. But how much gas is being produced? Well it's very difficult to quantify because the bubbles come out of thaw lakes, but Katey Walter from the University of Alaska, Fairbanks has used bubble traps to work out how much methane is emerging. It's enough to increase the methane contribution from the northern wetlands by up to 63%.

Katey - This work is all about quantifying a new source of atmospheric methane which was previously not recognised as a large and significant source, and that is bubbling from thaw lakes, lakes where the permafrost is melting and the lakes continue to expand as they melt into that permafrost, that's where they get the name thaw lakes.

Chris - So how have people tried to measure this in the past, or haven't they?

Katey - In the past scientists have measured methane emissions from lakes in two ways, they measure the diffusive emission where methane moves along a concentration gradient, from the sediments into the atmosphere, and they've done that by just measuring the concentration of methane in the surface water of the lakes. Another source of methane from lakes is bubbling, and that's a much more difficult source of methane to quantify because bubbling is very rare both in space and time.

Chris - So what have you done to get these accurate quantifications of them?

Katey - We have the excellent opportunity in Siberia to study bubbling because when the ice forms on the lakes in Autumn it's like putting a piece of Saran Wrap across the surface of the lakes, it traps the bubbles in place as they wobble to the surface and then they freeze into place in the ice. And we can walk across the ice and map out the distribution of point sources and hot spots.

Chris - So you walk out on the ice, you can see where the bubbles are coming up. But then how do you physically work out how much gas is there?

Katey - We've constructed bubble traps out of greenhouse plastic and copper wire and we place those either under the ice or in the summer when there is no ice we just place them floating under the water surface and each trap captures the bubbles that come up continuously. And so we would go out every day and measure the volume of bubbles that had collected.

Chris - So in the grand scheme of things how much methane is this actually contributing to the global environment?

Katey - Well, scaling up, the type of Siberian lake that we were studying, we estimate that methane emissions from these lakes is about 3.8 teragrams per year. Now, these lakes are only a portion of the northern lakes in general so if bubbling is something that happens everywhere then this could be an even much larger phenomenon than just the scope of our Siberia work. And now we see that just adding this small portion of Siberian lakes to the northern wetland emission estimate it increases it by up to 63%, ten to 63%.

Chris - So what are the implications if you add this to the global warming equation, then?

Katey - This is a new positive feedback to global warming. Methane is a very strong greenhouse gas and so as methane is being produced it is trapped in the atmosphere, increasing atmospheric warming which then enhances the thaw and the expansion of these lakes further. So today there are still about 500 gigatons of carbon remaining in this unique type of Siberian permafrost and it's projected that during the next century the majority of that will degrade and that can release tens of thousands of teragrams more carbon into the atmosphere.

Chris - So should this provoke a rethink of what we think is actually likely to happen in terms of global warming in the future, then?

Katey - Well, one component of the general circulation models that is missing is permafrost degradation, and especially with regards to the large pools of carbon that are stored in permafrost. That carbon content is still poorly known let alone these positive feedbacks to climate change that can happen from permafrost degradation. So yes, we do have a lot of rethinking and incorporation of these new sources.

September 2006

Strange Temperatures

Here is a way to entirely fool your senses using only three bowls of water. Have a go if you dare.

What you need

Three bowls or washing up basins large enough to put your hand in.

Warm water (NOTE - be careful not to make the water too hot!)

Cold water with a few ice cubes in it

Luke warm water

What to Do

What may Happen

When you put your hands into the medium temperature water, the hand that's been in the cold water feels warmer while the one that was in the warm water feels cold, even though they are both feeling water that is the same temperature.

What is going on?

It's because your senses are relative. They don't measure an absolute temperature or an absolute brightness of light; they make their measurements relative to the things around it. In the case of this experiment, the temperature sensors on your hands measure the temperature of the water relative to the temperature of your hand. If the water is warmer than your hand, it feels warm, and if it is colder than your hand, it feels cold.