Honeydew: The Food of the Ngahere
Our native forests – ngahere – have complex ecosystems. These ecosystems are under threat from introduced wasp species. In this episode of Project Mātauranga, Associate Professor Jacqueline Beggs shows us the life that resides below the surface in the forest and explains the work needed to restore the balance within these ecosystems.
Transcript
Dr Ocean Mercier
Māori have always been scientists, and we continue to be scientists. Our science has allowed us to live, work and thrive in the world for hundreds of years. My name is Dr Ocean Mercier, and I’m a lecturer in pūtaiao Māori at the Victoria University of Wellington. My job takes me all over the world to talk about Māori science and how traditional knowledge is being married with western science here in Aotearoa in order to find innovative solutions to universal global issues.
In this programme, we are going to show you how these worlds of science are intersecting and how the paths to our future are being formed.
Dr Ocean Mercier
I tino mārama ō tātou tūpuna, he mahi tā tēnā hanga, tā tēnā hanga o te wao. (Our ancestors were aware that every child of the forest had a role to play.) The birds, the trees, the rivers and even the insects were an integral part of the whole. This inter-relationship and synergy are understood by Ngāti Awa Professor Dr Jacqueline Beggs. She’s involved in the restoration of forest systems back to their natural habitat and has been studying the role of insects within ecosystems for the past 30 years. Engari, ehara i te mea, ko te mātai ngāngara te timatanga mōna. (But she didn’t start by studying insects.)
Associate Professor Jacqueline Beggs
Well my first research project was on kākā, our native forest parrot, and nobody had really studied those parrots before, and so the first thing was really just to go and have a look and see what are they doing in those forests. And it soon became apparent after following them round that they were feeding on honeydew. So honeydew is this byproduct produced by a native scale insect, and it’s just loaded with energy of course. It’s like coating your trees in high-energy fuel. And the kākā have a brush tongue and so they just run along the branches collecting all these little drops, and within a few hours, they can get all the energy they need in a day. So it soon became apparent that it was a really important resource for the kākā. Then the other thing that we started to notice that, in the late summer and autumn, that resource was being dominated by invasive wasps. So these wasps here completely monopolised the resource, they just remove so much of the honeydew. There’s nothing left for the animals – certainly not for the kākā. The kākā have to go and sort of subsist on whatever food is left in other areas, and it seemed that that resource was a really important part of the whole system that was being heavily impacted by introduced species.
Dr Ocean Mercier
Mohoa noa nei, kāore tonu te hunga whakatō ngahere taketake hōu i te mārama ki te mahi nui a nga ngāngara pērā i te ngō tarawai, me te mōrearea nui o ngā ngāngara i haria mai ai e te Pākehā ki tēnei whenua. (Even today, many people actively involved in the remediation of native forest don’t realise what an important role an insect like the honeydew bug plays or the threat posed by introduced insect species.)
Associate Professor Jacqueline Beggs
So inside the forests, you can see there’s a lot more diversity of trees. You’ve got a whole range of different species, and that’s providing the structure for the forests, and within that, we’ll have a whole range of different bird species coming in, the tūī and the pīwakawaka. But there’s a hidden story in there too, and it’s around the insects. Insects are really important for the cycling of the nutrients within forests, forming the soils, pollinating the plants and of course providing food for a whole range of organisms, not least our birds.
And here’s a good example of the sooty mould. So this is really thick, and if we look up, right up the top, if you peer, you’ll be able to see there’s a honeydew tree – so this kānuka laden with scale insects – and it’s dripping the honeydew down here, accumulating the sugar, and the sooty mould is growing up nice and thick. Inside this is a whole new world. Hidden underneath here, if I was to peel this off, you’d find all sorts of insects are using this as shelter and as a food resource. So it’s really important if we’re going to restore these systems that we also are thinking about restoring the insects and all the functioning that they bring to the systems.
So we have nine species of scale insect that are found just in New Zealand. Scale insects are tiny – I mean they range from very, very little to slightly bigger – but essentially, you need a microscope to see what’s going on. They don’t have legs because, for a lot of the stage, they are not mobile. They’ve got a mouth part that taps into the sugar system of the plant. They’re just really a bag that processes all that sugar, and out the other end, they’ve got a waxy anal filament, and that’s where they excrete these droplets of honeydew.
So here we are in a lovely bit of kānuka forest, and there’s scale insects all through this. You can see where they are because the black sooty mould, like just up here, is from the splash zone. So wherever the honeydew lands, that’s where the sooty mould is growing, and where you’ve got clean trunks, like just here, there’s no scale insects there dripping their sugar. So here’s a lovely bit just here, where there’s lots of scale insects. And if we look in here, it’s just thick with the scale insects, and these little white dots all along, that’s the actual scale insect, which has got sort of a hard capsule over it and the insect itself is hidden in there, but its mouth parts are into the sap vessels of the tree. So as the sap is coming along the tree, the scale insect is sucking the sap in, and then it’s pumping it out through the anal filament. So these white threads, they’re waxy, and they just keep growing out the end of the insect, and little droplets of honeydew accumulate at the end. So little drops of sugar are just the excrement of the scale insect. They are a free source of sugar for all sorts of organisms in the forest. So the birds love it, all sorts of insects like feeding on it. A lot of it just falls or is washed when it rains onto the ground, and then it just becomes part of the whole cycle of the forest, so it’s adding a whole lot of nutrient and affecting the decomposition and the nutrient cycling in the forest. So it’s part of the whole life force of the forest, and is I think it’s a really keystone resource, and what’s really cool about it is you can eat it. Oh it’s going to be very sticky, look at that, it’s like treacle.
Dr Ocean Mercier
Honeydew is a vital factor in maintaining the health of our forests. Our native birds, insects and mammals have always accessed this resource as part of the natural cycle of life in the forest. The honeydew insect draws sustenance from tree sap and expels the excess sugar as food for all the organisms of the forest. In breaking this symbiotic bond, wasps are wreaking havoc on our natural world.
Associate Professor Jacqueline Beggs
These forests must have been extraordinary in pre-human times. Not only was there honeydew dripping everywhere from the trees, but these forests would have also been full of seabirds. New Zealand was really interesting, because it was kind of like the seabird capital of the world. We see only kind of a fraction left now of what would have been here. So there would have been birds tumbling in at night, and they’re all burrowing in the ground and churning over the soil, but most importantly, they were bringing in nutrients from the marine system, and that means the system would have been laden with nitrogen that was coming in from the sea as well as having copious quantities of sugar from the honeydew. I can only just really imagine what it could have been like. For me, it’s very sad that we’ve lost that in New Zealand. If you go to an offshore island, in some special places, you get a wee taste of it still, but most of our mainland forests, it’s gone.
Dr Ocean Mercier
It’s clear from Jacqueline’s research to date that honeydew insects play a vital role in native ecosystems, which are under threat from introduced pests. With the balance of our natural world disrupted, developing the knowledge and capability to turn around the damage being done to our native forests is essential.
Ko te mahi nui a ngā ngō tarawai, he tukutuku kai kia ora ai ngā koiora o roto i te ngahere (Honeydew insects deliver a food that’s been vital in keeping the balance of life in our forests balanced), but today, introduced wasps are devouring the fruits of the honeydew bug and threatening the existence of our native plants, birds and insects – disrupting a system that’s been in harmony for millennia.
Associate Professor Jacqueline Beggs
OK, so we’ve got a kānuka forest here, so that’s relatively early stage in the succession as forest would come in and then the mature forest would eventually come up. So the forest has the plants as the basic structure, and then it would have a whole lot of insects that are providing food for native birds and things. Insects are also really important in recycling the nutrients as the leaf litter falls down. We’ve got predators and parasites coming in, and the main predators in these forests were the birds, they’re visual animals, and so all the invertebrates, their anti-predator responses were focused around birds. And when the mammals came in, it was open slather really. They just kind of cleaned it out. So things like the rats and the possums and the rabbits, they’ve all come in with Europeans. They feed on the native birds, they just completely removed a lot of those really important parts of the food web.
Bradford Haami
Me te ngāngara me nga mea katoa, no reira ra i roto i tēnei whakapapa na Tāne, ka puta ko ētahi o nga ngangara nga punga, ētahi o nga ngāngara weriweri, pera i te weta. Na Haumia tera te tīpuna atua nei o nga rarauhe me nga aruhe, engari ra he wai roa, he namu, he ngāngara i hekemai nei ia Haumia, no te mea ko te nohoanga o ērā ngāngara e nohomai nei i roto i te rohe o te rarauhe. (Insects and everything else, its genealogy begins with Tāne. We have insects like the spider, the more offensive insect like the wētā. Haumia, the god of the uncultivated plants like the fern and the edible fern root, as well as the mosquitoes, the sandflies are all descendants of Haumia, and the habitat of those types of insects is the fern.)
Whiro te atua nei e ngau kino i roto i te ao tūroa, na mea kino, nō reira ra ko nga - e maha nei ngā namu, me ngā pekepeke me ngā – iwi o ngā ngāngara, hei ope tū tauā mo Whiro. (Whiro, the god of the underworld, presides over the environment, particularly the bad insects, and so we have millions of sandflies, insects and spiders – they’re the army of Whiro.)
Dr Nick Waipara
So our natural environment, our forests, our waterways, they’re under attack by huge pest burden. You know, the big things such as your possums, your rats, your stoats. But it’s also the little things, it’s things like ants and wasps. They’re really coming into our forests and waterways and having untold impacts on our native invertebrates for example. The little insects, what’s happening to them? You know, it’s right from feeding from the canopy right into the soil ecosystem. It’s being affected by this massive threat of pests, for example, here you can see the African club moss invading the ngahere into the forests. You know, what’s happening underground? What’s happening to our native beetles? It’s that sort of knowledge we don’t even know yet. We don’t even know what we’re losing in some of our forests and waterways. So, it’s a real huge attack on our whole natural environment, and we have to get our heads around and get more science into how do we – what are we losing and how do we control it.
So our pest management work not only comes from the forest but into our farmland, our orchards, a huge commercial impact of pests. For example, our dairy farmers having to contend with weeds such as ragwort, Californian thistle – huge economic losses to our dairy production. And then you think about TB, being infected by the invasive possum. You know, huge untold impact on our rural communities, so these pests not only impact on our economy but also our social and cultural values.
Associate Professor Jacqueline Beggs
So imagine this trunk was covered in the scale insect and honeydew all over it. If you go onto an offshore island that has high densities of gecko, such as Korapuki Island in the Mercury Islands, and you come out at night, then these trees are just festooned with geckos. So the Duvaucel’s gecko, which is a big chunky gecko, you come up to a tree, and you know, you can sort of, you know, there’s 20 or more up the tree. They’re just extraordinary. You don’t see that on the mainland, and that’s because the mammalian predators are eating them out. So really, if you wanted to restore these systems, you’ve got to get rid of those mammalian predators, and if you want to restore the honeydew as well, you have to deal with the wasps. So we have multiple problems, and it’s all interconnected, and you know, there’s just such a lot of work that we need to do if we want to start putting the mauri back into these forests.
Bradford Haami
He mea kino tēnei āhuatanga nei o te tū hanga raina, i te mea he maha ngā tāngata, he maha ngā para i rere atu nei ki ngā awa, ki ngā ngahere, ki te moana, kia whakamate i ngā kararehe o – me ngā rakau o wēra rohe katoa. No rēira me whakaro nei tatou, me pehea te haere o te tāngata i roto i tēnei ao i runga i tēnei ao tū roa, kia whakaora ai te ngahere, te moana, me te whenua. (This is a bad impression being made because there’s so many people, waste products flow into the rivers, the forests, the seas, that kill our animals and the trees in those areas. We have to think about how man can move around on this Earth and around the environment to make the forest, the land and the sea safe.)
Associate Professor Jacqueline Beggs
We don’t actually know all that much about many of our native insects, but we do know that there are some species that we really don’t want in New Zealand, and these are some of them here. This is the common wasp. I think this is probably a relatively small nest, because you can see from the number of wasps coming in and out that there’s not that much of a nest underneath. We don’t really have any good ways of controlling this. If I just wanted to get rid of one nest, no problem, I can just use a contact poison and we can deal with it. The problem is, there’s so many nests in the forest that that’s not going to work on a large enough scale to do any real good to the ecology of our forests. So we’d like to use poison baiting or a biological control agent or some other way of dealing with them on a widespread scale, but we really don’t have the tools yet that we can do that. And the problem is – I mean, this is a small nest – imagine if this nest, and I’ve seen them this size, 2 metres high, this round, imagine the impact that they would be having on the forest.
Well, you can see here, we’ve got a couple of different ways of trying to control pest species. This bottom one is for rodents, particularly rats, and that’s baited with a cereal bait and brodifacoum. That’s really effective, and if you put them out enough and operate them right through the peak of the rat-breeding season, then you get really good control. So we can do that well.
And just over there is a stoat trap. And the stoats, trapping is relatively successful. Wasps are a bit more of a problem. We don’t currently have a product that is available in New Zealand for controlling wasps. These were put out so we could toxic bait them, and so if you can get wasps coming in and taking the protein, which they love, and it’s mixed with a poison, then they’ll carry it back to the nest and the poison will get passed around inside the colony and you’ll bowl the nest. We know that works really well. When we were doing trials, many years ago, we were getting 99% kill of all the wasp colonies.
The issue has been to get something registered, and so the poison that we were using, fipronil, is really effective, but there were issues with its use overseas, and they were really concerned about effects on honey bees. Now the way we use it isn’t at all an issue for honey bees, because it’s a protein bait. That wasn’t good enough for the company. They just didn’t want their product associated with killing a social insect. So that’s off, you know, the horizons really. We can’t go that route, and we need to start looking for other options.
Dr Ocean Mercier
In the fight for the survival of our forests, introduced pests, particularly wasps, have secured a niche that goes unchallenged, and in doing so, they are forcing us to adapt and innovate to restore the natural balance. But it’s a fight that restoration experts like Jacqueline Beggs are determined to win.
I roto i ngā tau nei, kua taetae mai ngā ngāngara o tarawāhi ki ō tātou rauwiringa kaiao (Our recent past has seen the colonisation of Aotearoa’s ecosystems by introduced organisms), unsettling the delicate balance of our native forests. Knowledge of our forests past as well as what’s happening today is crucial in addressing the issue, and understanding the vital role that our native insects play, pērā i te ngō tarawai (particularly the honeydew insect), is one of the key elements in helping to find a solution.
Associate Professor Jacqueline Beggs
Wandering through the forests like this, you start to get an appreciation of the amazing nature of the forests, and it’s understanding not just what puts big trees like this here but what makes the whole system function, and I think the invertebrates have a really key role in that. So you can see the leaf litter starting to build up around this tree, but without the invertebrates, I mean it would be a mile high. So there’s a whole lot of different species that would be shredding the leaves, chewing them up and making them into a form that the fungi and the bacteria can get in, and that’s what turns over the nutrients in the forest.
We have such huge gaps in our knowledge of the forest system, but mātauranga Māori would help us fill in the gaps. I mean, they would have understood and appreciated what some of these insects were doing. You couldn’t have a close association with the forest like Māori would have and not noticed some of the things that were going on. So when something like rātā flowers, I mean those beautiful crimson flowering that you get up high, some species of native bees would be coming in, feeding on the nectar and the pollen and pollinating it. I mean, this part of the forest, you can feel the mauri of the forest, and if we could patch that together will the mātauranga Māori, then we would really start to have an understanding of how these systems work.
Dr Nick Waipara
Our restoration work really starts with places like this – bare ground, grassland – we want to reforest bare places like this. And that takes a whole involved process, which we’re learning more about all the time. So in behind me here, you see the harakeke, the mānuka, the kānuka that we start with level one restoration. And then what we’re trying to do with that is bring back the amazing canopy forest that you’ll see on the ridgeline over here. And so that whole restoration principle involves not only planting the canopy trees, but it’s also bringing back the birds. But beyond that is the whole ecosystem, the health of that forest, and that’s where the honeydew, scale, all the little invertebrates in the forest floor, we need those back too, because it’s a whole holistic ecosystem that the ngahere needs to be healthy. And that’s where Jacqueline’s work’s quite absolutely pivotal. It’s informing our restoration about how these little things work.
Associate Professor Jacqueline Beggs
We’ve got a long way down the track of knowing what to do for restoring some elements, so we can get back to a beautiful system like this. We know about the plants we need to be planting, we’re starting to get a handle on how to get the birds back, but I think one of the key gaps we still have is around the invertebrates. We actually are really at the baby steps of understanding what we need to do to be restoring invertebrates. So now work has identified one gap, which is around the honeydew scale insect. And if we could put that back into our restorations as well – because they’re poor dispersers and would get there really slowly on their own – if we put them back at an earlier stage in the restoration process, then we would be putting some of those key interactions back that would be food for the birds and other insects and for the geckos, and it would start the nutrient cycling happening the way it should. So it would really start to build the whole flourishing system in a way that we hopefully have got back here.
Bradford Haami
Ko ngā ngāngara i hāere mai nei i tauiwi, a, he manene, ko ēra e whakamate i te ahuatanga nei i tēnei whenua. No rēira ra, ko ēra mea iti iti he manene e ngau kino nei, e kai ana nei, ngā mea iti iti nei o tēnei whenua. Me patai atu nei mātou, me pēhea e tiaki nei ēra mea, ki a ora ai to mātou nei whenua me ngā karahere tūturu nei o tēnei ao? (These insects were brought here by the Europeans and foreigners. They destroyed the character of the land and so these minor complications – foreign – are destroying the land. We have to ask the question how can we protect these things to safeguard our land and the native animals of this country?)
Dr Ocean Mercier
He mahi tino nui kei mua i te aroaro, ki te kimi rongoā mō ngā raruraru, nā ngā kararehe hōhā o tāwāhi i kawe mai. (We have a huge task facing us to overcome the problems that introduced pests have brought to our shores.) The work of Dr Jacqueline Beggs provides a glimmer of hope as we seek greater understanding of the interactions of Tāne, Punga, Haumia, Peketua and Whiro.
Western science provides one pathway to the solutions required, but we must uncover and integrate the knowledge from our past so that mātauranga Māori can take its place in restoring the realm of Tāne to the natural balance it once knew.
Acknowledgements Video courtesy of Scottie Productions. © Scottie Productions, 2013.
