This week I’d like to give you an introduction to the history and ecology of the dingo (Canis lupus dingo), but I’m not sure how thorough I can be here- one of the things that struck me in my reading was how many opinions there are about dingoes. And people with differing conclusions seem to be responding to each other in print- one study says one thing, the next study says that the first did not collect data properly, a third says the second did not use the most appropriate process for analysis; an article is published, and then someone else publishes a letter in response. So it would seem that dingoes are controversial subjects- I am neither a dingo expert nor a statistician, but I’ve had to make decisions about what to include here; hopefully I’m offering a reasonably accurate account of this canid species.
Dingo (Canis lupus dingo)
Basic dingo ecology. These 30-35 lb. predators can be solitary or found in groups, and the size of the group is related to how big the prey is (which makes sense- if your prey is big, like a large kangaroo, you may want some help to ensure a successful kill and there will be plenty of food to share at the end of the day, but if you are going after a rabbit, you may not want dinner company) (Vernes et al. 2001). Dingoes are flexible predators who eat a wide variety of prey species and can alter their behaviors to take advantage of changes in food supply, such as focusing on rodent species during population booms and then diversifying their diet when the boom is over (Pavey et al. 2008).
What does dingo family history look like? There is general agreement that dingoes arrived in what is today mainland Australia between 5000 and 3500 years ago (Johnson & Wroe 2003, Stephens 2011), probably as a semi-feral, semi-commensal element of Aboriginal society- based upon the low genetic diversity of dingoes, it’s likely a few individuals founded the entire population. Dingoes have been given responsibility for the extinction of a number of native Australian species on the mainland (and there is also a debate about whether to consider dingoes native or exotic animals), including the thylacine and Tasmanian native hen, but researchers have begun to question those claims, partly because the thylacine was a predator that could take down larger prey than a dingo while the hen was likely the prey of neither predator, and partly because the dingo’s arrival coincided with a drier climate that would have put stress on many species (Johnson & Wroe 2003). With the arrival of Europeans and, specifically, European livestock, dingo-human conflict became a big issue. In 1885 dingoes were officially labeled pests and a bounty system implemented (Allen & Sparkes 2001). To-date more than 1.5 million bounties have been claimed; baiting with poison and shooting trapped animals were and are the most common methods of population control. Do they deserve this treatment? Well, that is the crux of the dingo debate in many ways. There is no question that dingoes have killed and continue to kill sheep, which is damaging to people’s livelihood. They also prey upon some of Australia’s threatened and endangered species- although that may have been normal behavior for several thousand years, it tends to get different reactions when the prey species is in danger of extinction. There are other viewpoints which say that dingoes are beneficial in the environment because they keep other pest populations down (Allen & Sparkes 2001) or because their presence helps small mammals by keeping their predators away (Letnic et al. 2009) (more about this in a later post).
What does the dingo’s world look like today? The species’ range is smaller, and across Australia dingoes are treated differently in different locations (Levy 2009)- in some places they are protected and in others rural landowners are required to kill them. Starting in 1945, the Dingo Barrier Fence (DBF) was constructed along part of the border between New South Wales, South Australia, and Queensland with the idea of keeping dingoes out of sheep ranching lands (Allen & Sparkes 2001). This 2-m tall fence has been the subject of many dingo studies because it offers the chance to examine the differences between areas with dingoes and areas without them (and this is where I found a variety of contradictory opinions). Keeping dingoes out of sheep areas has reduced sheep-predation, but people have also noticed that there are more red and grey kangaroos on the dingo-free side of the fence (Caughley et al. 1980; Pople et al. 2000); the opposite is true for rabbits and rodents (Letnic & Koch 2010). One of the big dingo debates centers around why this is so: according to Pople et al. (2000) and Letnic & Koch (2010), dingoes are keeping the roo numbers down through direct predation; according to Newsome et al. (2001) the differences are caused by fewer watering holes and less preferred kangaroo habitat; and according to Caughley et al. (1980) high rabbit densities give dingoes adequate alternate prey to keep predator numbers high enough to depress kangaroo populations (I had to think about that one for a while before I understood what they were saying: normally when a predator hunts a species until the prey numbers drop substantially, the predator has just lost its main food source and it also declines, like the mink downstream from me who spent a lot of time fishing in one section of river until bigger fish became scarce and then had to pack up camp, but the rabbits in Australia gave dingoes another food source, so the dingo population didn’t decline when kangaroos did). There are also concerns about dingoes hybridizing with feral dogs, especially along coastal areas in the southeast (Stephens 2011), so researchers aren’t sure exactly what percentage of the dingo population is ‘pure’, which can complicate how we approach dingo roles and management in the future. Why is this important? Well, if people are already lukewarm about an animal whose numbers have declined and then someone claims that the remaining population genetically isn’t that species anymore, you tend to lose support for conservation measures.
I recognize that the information above is a lot to take in, and I haven’t even scratched the surface in some respects, but hopefully I’ve given you a better sense of the dingo’s history and possible ecosystem roles. Next week I’d like to look at how the dingo may or may not fit into Australia’s conservation plans, and also peek into how the dingo’s situation relates to that of other wild dogs around the world. The presence of any wild dog in an ecosystem can be very controversial, so I have no doubt that there will be multiple viewpoints about those as well.
Works cited:
Allen, LR & EC Sparkes. 2001. The effect of dingo control on sheep and beef cattle in Queensland. Journal of Applied Ecology 38: 76-87.
Caughley.G, Grigg, GC, Caughley, J, & GJE Hill. 1980. Does dingo predation control the densities of kangaroos and emus? Aust. Wildl. Res. 7: 1-12.
Johnson, CN & S Wroe. 2003. Causes of extinction of vertebrates during the Holocene of mainland Australia: arrival of the dingo, or human impact? The Holocene 13: 941-948.
Letnic, M, Crowther, MS, & F Koch. 2009. Does a top-predator provide an endangered rodent with refuge from an invasive mesopredator? Animal Conservation 12: 302-312.
Letnic, M & F Koch. 2010. Are dingoes a trophic regulator in arid Australia? A comparison of mammal communities on either side of the dingo fence. Austral Ecology 35: 167-175.
Levy, S. 2009. Dingo dilemma. BioScience 59: 464-468.
Newsome, AE, Catling, PC, Cooke, BD, & R Smyth. Two ecological universes separated by the dingo barrier fence in semi-arid Australia: interactions between landscapes, herbivory and carnivory, with and without dingoes. Rangel. J. 23: 71-98.
Pavey, CR, Eldridge, SR, & M Heywood. 2008. Population dynamics and prey selection of native and introduced predators during a roden outbreak in arid Australia. Journal of Mammalogy 89: 674-683.
Pople, AR, Grigg, GC, Cairns, SC, Beard, LA, & P Alexander. 2000. Trends in the numbers of red kangaroos and emus on either side of the South Australian dingo fence: evidence for predator regulation? Wildlife Research 27: 269-276.
Stephens, D. 2011. The molecular ecology of Australian wild dogs: hybridization, gene flow and genetic structure at multiple geographic scales. PhD thesis: University of Western Australia.
Vernes, K, Dennis, A & J Winter. 2001. Mammalian diet and broad hunting strategy of the dingo (Canis familiaris dingo) in the wet tropical rain forests of northeastern Australia. Biotropica 33: 339-345.
I’ve spent the last few days going back and forth in my mind about this month’s topic. I am fascinated by canids (and quite amazed, when I look at my dog, to think of her progenitors), and there are so many species to choose from- I wanted a topic that was outside of North America since so many of my posts tend to focus on my own continent, and I enjoy learning about as many things as possible, so I wanted to pick something that was very new to me. I think that people around me tend to think foxes and wolves when they hear the term ‘canid’, and that only gets you so far.
Dingo (Canis lupus dingo)
For a day or two I was in the middle of a dingo-dhole debate, neither of which is familiar to me. These species found in Australia and Asia are each appealing in their own way- dingoes are connected to traditional lore and modern suspicion, and dholes are quite the mystery in some ways. The dingo won out to a certain extent, and that’s where my focus will be, but I also hope to broaden the discussion at times to include other wild dogs.
What I know about dingoes is pretty basic: I believe that they came to Australia when humans first arrived- they are not marsupials, unlike most of the other mammals there; there has been friction between sheep ranchers and dingoes because the latter are the top predators in their environment; and, there has also been concern over the danger that dingoes pose to people. I know that Australia is dealing with both exotic species issues and concerns over water supply, and I’m curious to learn about how the dingo fits into and is impacted by those situations. I’m also curious to learn about the ways that dingoes fill important ecosystem roles-I think that sometimes people concentrate on the perceived negatives of having predators around them and forget that ecosystem processes depend upon their presence.
Over the next few weeks, I hope to provide some ecological background on the dingo as well as looking at what researchers are learning about their situation and prospects today. Whether you are a wild-dog lover like me or not, stay tuned for a journey down under.
I don’t want this to become an unusual scene where I live.
Over the last few weeks, I’ve been looking at the possible impacts of climate change on temperate forests around the world, impacts that could disrupt forest dynamics and alter the landscapes around us. Rising global temperatures can rearrange precipitation patterns, warm soils, and cause expanded disease and pest outbreaks. And there are concerns that tree populations will not be able to migrate quickly enough to respond to changing climatic conditions. I’m already quite frustrated that the lilacs around me, which once bloomed for my birthday at the end of May, now bloom considerably before my birthday; the idea that local paper birches may not be able to handle future warming temperatures is worse. But there are several things that we all can do to support trees, as well as all plant and animal communities, as things heat up and patterns change.
Getting active outside:
Looking at the big picture:
- Our parks and forests were often created because of the particular beauty or species richness of a specific location, but some of these places will become less than ideal homes for species as global conditions change. One of the challenges species will face is how to get from where they are to a more suitable location, sometimes because they cannot move on their own and sometimes because the area they would be moving through is already occupied by us. Connective corridors can provide a safe route from one place to the next, but only if we make sure those corridors exist- talk to your local and state conservation officials about the corridors (or lack thereof) where you live and how you can support the creation and maintenance of them. In temperate eastern Australia, corridors are an important element in dealing with the drier conditions to come (Mansergh and Cheal 2007).
Every little bit helps:
- Look for wood products with the Forest Stewardship Council (FSC) label- businesses that participate in this program follow production and oversight guidelines designed to protect forest resources, local communities, and environmental processes.
- I’ve said it before with regard to migrating bird populations, but shade-grown coffee is a good choice in the supermarket- it increases tree cover and offers habitat to other species. Farmers with other products are also starting looking at the shade-grown model, so keep a look out for that designation in other places.
- Reduce your emissions through reduced driving, slightly lower thermostats in winter, etc.- we may not be able to stop global warming, but we may be able to slow it down a bit, giving plants and animals more time to adapt.
Works Cited:
Aitken, S.N., Yeaman, S., Holliday, J.A., Wang, T., and S. Curtis-McLane. 2008. Adaptation, migration or extirpation: climate change outcomes for tree populations. Evolutionary Outcomes 1: 95-111.
Locatelli, B., Evans, V., Wardell, A., Andrade, A., and R. Vignola. 2011. Forests and climate change in Latin America: linking adaptation and mitigation. Forests 2: 431-450.
Mansergh, I. and D. Cheal. 2007. Protected area planning and management for eastern Australia temperate forests and woodland ecosystems under climate change- a landscape approach. In: Protected Areas: buffering nature against climate change. Proceedings of a WWF and IUCN World Commission on Protected Areas Symposium, 18-19 June 2007, Canberra. (eds. M. Taylor and P. Figgis) pp. 58-72. WWF- Australia, Sydney.
If the trees on the hillside succumb to water stress, the bushes and grasses down below may find their world contains more water than they can handle.
As I mentioned in my last post, predicting the form of future forests is complicated due to the wide variety of factors involved, but there are some common concerns that researchers share about the challenges trees will face with global climate change. Changes in temperature and precipitation patterns will alter the suitability of forest locations (and not always in the ways you might think- in the Netherlands, for example, summer precipitation is expected to decrease while winter precipitation is expected to increase (Brolsma 2010)- because water access is typically greater downslope than upslope, researchers predict that summer water stress will cause thinning of vegetation upslope, which you might expect. But, as a result of more winter precipitation and fewer plants upslope to absorb moisture, they expect wetter conditions downslope and a change in species composition in response. I find this situation amazing- too little water in summer will lead to too much water in winter- and those species that can handle the drier summer conditions may not be able to adapt to increased moisture).
Will trees be able to find the areas that work best for them? Scientists have been looking at this issue from several angles, not all of which have rosy scenarios. Tree populations contain high levels of genetic diversity which can help them adapt to changing conditions, but when a changing climate encourages genetic variability, it is possible that none of the new variations will be particularly well-adapted and you can see high juvenile mortality as a result (Kremer et al. 2012). With an increase in temperatures, we could expect that temperate forests would move away from the heat and into areas that had previously been cooler- Kremer et al. (2012) felt that trees growing along the line of expansion in the northern hemisphere would benefit from ‘pre-adapted’ genes coming from trees in the south already prepared for a certain degree of heat, but those trees along the southern edge of the range would be at a disadvantage when dealing with even hotter temperatures. How quickly can tree populations shift location? That is one of the big questions- based on previous changes in the earth’s climate, we know that forests can expand and contract in response to warmer and colder climates, but we’re not sure if they can keep up with the changes in store this time around. Models predict that climatic zones may shift as much as 150 km over the next century (see the European Commission’s Dept. of Agriculture for 2008 reports on how climate change is expected to impact Europe’s forests), but pollen analysis suggests that migration rates after the last ice age were 100-200 m per year (Aitken et al. 2008). At that rate, forests could shift up to 20 km in a century, but not nearly enough to keep pace with climate change. Aitken et al. (2008) suggest that, by 2050, if we experience a mid-level climate change scenario, as much as 38% of plant species could be extinct.
It’s likely that a picture of this location in Franconia Notch State Park will show a different plant community in 50 or 100 years.
So what will our forests look like? It’s a little difficult to predict this exactly, but here are the general trends:
- Forest fire events will likely become more common and severe in areas along the Mediterranean, southeastern Australia, and western US, and fire suppression techniques may lose some of their effectiveness (Keenan 2012; Loehman et al. 2011).
- Northern Europe will see increased forest growth, while southern Europe experiences decreased forest growth (Kolstrom et al. 2011).
- In eastern North America, species composition of forests will change as some, such as paper birch, flee higher temperatures and others, like beech, have problems with water stress (Thompson et al. 2009- if you live in this area and would like to see what the future possibilities are, check out my Just Fascinating Stuff page for a link to prediction maps by species, state, and region).
- Forests will experience an increase in disease and pest outbreaks, such as mountain bark beetles which are projected to spread 7° farther north with a 2.5° C increase in temperature (Cudmore et al. 2010).
- Species composition in general may change as habitat conditions alter- there is concern, for example, that the northern flying squirrel (Glaucomys sabrinus) may become rare or disappear from the southern part of its range due to habitat loss from both human and climatic changes to the landscape (Weigl 2007).
So this generally sounds like there are big problems over a wide area, but we know that forests have endured and overcome past climatic shifts, and we know that there are people working to address these issues- there is hope for the future of the forests. Next week I’ll be looking at ways we can mitigate and adapt to climate change impacts, so that we can all pitch in and give trees a hand.
Works cited:
Aitken, S.N., Yeaman, S., Holliday, J.A., Wang, T., and S. Curtis-McLane. 2008. Adaptation, migration or extirpation: climate change outcomes for tree populations. Evolutionary Outcomes 1: 95-111.
Brolsma, R.J. 2010. Effect of climate change on temperate forest ecosystems. Netherlands Geographical Studies 396: 1-157.
Cudmore, T.J., Bjorklund, N., Carroll, A.L., and B.S. Lindgren. 2010. Climate change and range expansion of an aggressive bark beetle: evidence of higher beetle reproduction in naïve host tree populations. Journal of Applied Ecology 47: 1036-1043.
Keenan, R.J. 2012. Adaptation of forests and forest management to climate change: an editorial. Forests 3: 75-82.
Kolstrom, M., Lindner, M., Vlien, T., Maroschek, M., Seidl, R., Lexer, M.J., Netherer, S., Kremer, A., Delzon, S., Barbati, A., Marchetti, M., and P. Corona. 2011. Reviewing the science and implementation of climate change adaptation measures in European foresty. Forests 2: 961-982.
Kremer, A., Ronce, O., Robledo-Arnuncio, J.J., Guillaume, F., Bohrer, G., Nathan, R., Bridle, J.R., Gomulkiewicz, R., Klein, E.K., Ritland, K., Kuparinen, A., Gerber, S., and S. Schueler. 2012. Long-distance gene flow and adaptation of forest trees to climate change. Ecology Letters 15: 378-392.
Loehman, R.A., Clark, J.A., and R.E. Keane. 2011. Modeling effects of climate change and fire management on western white pine (Pinus monticola) in the northern Rocky Mountains, USA. Forests 2: 832-860.
Thompson, I., Mackey, B., McNulty, S., and A. Mosseler. 2009. Forest Resilience, Biodiversity, and Climate Change: A synthesis of the biodiversity/resilience/stability relationship in forest ecosystems. Secretariat of the Convention on Biological Diversity, Montreal. Technical Series no. 43, 67 pages.
Weigl, P.D. 2007. The northern flying squirrel (Glaucomys sabrinus): a conservation challenge. Journal of Mammalogy 88: 897-907.
I’ve spent the last week enmeshed in the intricacies of climate change research and trying to understand how temperate forests will be impacted- and there were quite a few more variables than I had been anticipating. I guess I had assumed that warmer temperatures would mean shorter winters, earlier springs, and probably more bark beetles, and that was about it. Instead, I learned that trees would be impacted by more than just warmer days, and the results will really depend on more than just temperatures. What I’ve put together below is meant to provide a little background on the situation.
Each species will respond differently to climate change- which will be the most successful?
How will rising temperatures alter forests? Well, there are still a few unknowns with this, but the general trend is longer growing seasons and increased plant growth (Saxe et al. 2001). Warmer days will also mean warmer soils. So that’s a good thing, right? Well, it’s a bit of a tricky situation, because some plants and some natural processes operate better at lower temperatures (this is why, for example, lilacs won’t make it in Georgia, much to the disappointment of a woman I know). In addition, when scientists forecast overall warmer temperatures, they are usually working with averages, but, as anyone who was on the East Coast over the last 2 weeks can tell you, extreme weather events seem to be a bit too common for comfort and extreme temperatures go along with that. It’s true that longer growing seasons can mean bigger plants, but there are concerns that earlier springs and later autumn frosts will cause communication errors for trees responding to seasonal changes (Saxe et al. 2001). Trees develop cold-hardiness for winter based upon temperature and daylight cues, and then use those same cues to start the growing season in the spring. If the timing of those cues is out of sync, trees may not prepare for winter adequately, or they may come out of dormancy too soon and risk frost damage (Aitken et al. 2008). If they then experience an extreme weather event, such as the recent nor’easter, they could face damage or even death. Another concern is that trees which depend more on daylight than temperature cues could function at a disadvantage and be out-competed by other species taking better advantage of the longer growing season. What about warmer winter temperatures? One worry here is how precipitation will be affected (see below), but another issue is that warmer days during winter can cause trees to dry out. When conifers were subjected to higher winter temperatures without an increase in light, some lost their needles (Saxe et al. 2001).
What about warmer soils? As it turns out, soil temperature, soil moisture, and soil nutrients will all play a big role in how forests react to climate change. Typically, the warmer the habitat, the more equal the distribution of carbon between living biomass and soil (Malhi et al. 1999), so, as temperate and boreal areas warm up, you may find increased soil respiration and nutrient cycling; soil carbon stocks will go down and more carbon will be stored in living tissue. At the same time, soils in some areas may become drier and some studies have predicted increased water stress for plants under those conditions (Aber et al. 1995). This could be caused by changes in where precipitation falls, but also changes in what form it takes- if warmer winter temperatures mean that less snow and more rain falls or if snow melts faster in the spring, trees may not have access to enough moisture later in the year (Weltzin et al. 2003). Given their stationary nature, they can’t go looking for better conditions, but will simply have to make do.
These trees are prepared for and, in some ways, depend on cold winters with lots of snow- but they may not be ready for greater extremes in the future
Should we expect changes in the forests around us? Once again, this is a difficult question to answer- so many reports commented that each species and each location was an individual case because of differences in tolerance, nutrients, water-cycling, etc. Pastor & Post (1988) felt that spruce forests in northern Quebec would continue as such despite the impact of climate change, while forests from the west of the Great Lakes to the Atlantic would become mostly northern hardwood at the expense of spruce and fir. One of the big questions is which species will adapt best to new conditions and which will be unable to compete. And there are concerns over how pests and diseases will be influenced by climate change- warmer winters could mean more bark beetles, warmer and wetter summers could cause fungal and disease outbreaks, but higher carbon dioxide levels might cause leaves to become less nutritious for insects and limit their numbers (Saxe et al. 1998).
I feel that the future composition and health of forests as climates around the globe change is a big topic that needs more investigation and discussion, so that will be my focus for next week, as well as a peek into changes in animal populations as a result of shifts in vegetation. There are ways to research future changes, but the complexity of the systems involved and the sheer number of variables mean that some consequences of a warmer climate are not yet known. Hopefully, however, we can get of sense of the general trend and then refine our understandings with more study.
Works Cited:
Aber, J.D., Ollinger, S.V., Federer, C.A., Reich, P.B., Goulden, M.L., Kicklighter, D.W., Melillo, J.M., and R.G. Lathrop, Jr. 1995. Climate Research 5: 207-222
Aitkin, S.N., Yeaman, S., Holliday, J.A., Wang, T., and S. Curtis-McLane. 2008. Adaptation, migration or extirpation: climate change outcomes for tree populations. Evolutionary Outcomes 1: 95-111.
Malhi, Y., Baldocchi, D.D., and P.G. Jarvis. 1999. The carbon balance of tropical, temperate and boreal forests. Plant, Cell and Environment 22: 715-740.
Pastor, J. and W.M. Post. 1988. Response of northern forests to CO₂-induced climate change. Nature 334: 55-58.
Saxe, H., Cannell, M.G.R., Johnsen, O., Ryan, M.G., and G. Voulitis. 2001. Tansley review no. 123: Tree and forest functioning in response to global warming. New Phytologist 149: 369-400.
Saxe, H., Ellsworth, D.S., and J. Heath. 1998. Tansley review 98: Tree and forest functioning in an enriched CO2 atmosphere. New Phytologist 139: 395-436.
Weltzin, J.F., Loik, M.E., Schwinning, S., Williams, D.G., Fay, P.A., Haddad, B.M., Harte, J., Huxman, T.E., Knapp, A.K., Lin, G., Pockman, W.T., Shaw, M.R., Small, E.E., Smith, M.D., Smith, S.D., Tissue, D.T., and J.C. Zak. Assessing the reponse of terrestrial ecosystems to potential changes in precipitation. BioScience 53: 941-952.
At the base of Mt. Washington, paper birches start to strut their stuff
Despite the short days, I really enjoy November in New Hampshire, partly because it feels like things are slowing down a bit and partly because, with the leaves gone, I can see the trees themselves now. In the summer I appreciate the green shade provided by trees, I love the colors of fall, and I will be very excited to see leaf buds in spring, but sometimes I forget what is holding all of those leaves up- and this time of year reminds me just how much I love looking at the trunks of birches.
I appreciate the trees around me for several reasons: they are beautiful to look at, they provided habitat to wildlife, they take in carbon dioxide in exchange for oxygen, and the products we get from trees are quite helpful. As a NH native, I would be remiss if I neglected to mention just how much joy maple syrup has added to my life (yesterday’s apple pie is just one piece of that). I find deciduous trees particularly appealing because their appearance changes so much from season to season.
When Hurricane Sandy came through a few days ago, we sustained minimal damage in part because the leaves had already fallen and branches were free to twist and turn as needed. Had this storm been earlier in the year, like Irene, it would have been worse for us. I’ve heard people talk about more extreme weather events as the climate changes which could be a future problem for both us and the trees. But global climate change can have other effects on trees as well, so I’m curious to learn about concerns scientists have for the future of our forests, specifically the temperate forests that are nearest to my heart. This month I will be investigating the relationship between climate change and tree survival. This is a topic that I know very little about (I know that maple syrup production has been shifting north, but I’m not sure how much of that is acid rain and how much is climate change; I know that paper birches are at the southern limit of their range here, but I don’t know how much conditions need to shift before they start having problems; and I know that there are concerns for species who have already retreated to mountain tops), and I’m not sure how much research is available, but I’m going to see what I can find and look for ways to aid trees as conditions around them change. I don’t expect to be the Lorax, but I’m hopeful that I can get a better sense of what is happening and how we are/can be involved in the path from here.
So join me for a walk through the woods and current conservation research on forests.
As I looked for ways that we all can get involved in elephant protection, I kept coming upon the same request- “Donate Now”- and, in some ways, that was very disappointing because I was hoping to get more directly involved. But, after investigating some of the issues in elephant conservation, I began to feel this was a request that needed to be responded to in a thoughtful manner. In quite a few ways, saving elephants is about money- in some areas, park rangers have gasoline for poaching patrols because people made donations; enlarging reserves to prevent environmental damage from too-dense populations takes money; Blignaut et al. (2008) calculated that Masai farmers in Amboseli NP lost $10/acre in crops per year to elephants. And, although it may seem as if only huge donations can make a difference, some costs aren’t that monumental- when Blignaut et al. (2008) applied their calculations to all farmers in Africa who face elephant damage to crops and then divided that amount by the number of families in the Western world, it worked out to a yearly contribution of ̴60¢ per family; from that perspective, fostering goodwill by reimbursing farmers for elephant damage seems pretty reasonable. And I do think it’s important to consider what we, individually, are willing to give to ensure the survival of elephants in the wild. I can say that I support elephant conservation all I want, but, at the end of the day, I don’t have to live with them or experience their direct impact on my life- if I want people in elephant habitats to be tolerant of the giants in their midst, I think it’s only fair that I also pitch in and feel some indirect consequences of elephant conservation in my wallet.
Donations can be personal. Although conservation organizations are quite happy take your donation with no strings attached, there are ways that you can specify what you want that money to do. Both the Nature Conservancy and Save Nature have ‘Adopt an Acre’ programs; in the latter you can choose which park to support. Many people are also familiar with the ‘Adopt a Wild Animal’ programs that funnel donations into species conservation programs (for example with the World Wildlife Fund). But you may also want to think about other ways that money can be used. One theme that was mentioned again and again by conservation foundations working in Africa and Asia was educational programs, especially for children living near conservation projects. By providing educational opportunities and the supplies needed to take advantage of them, you can both help communities become better prepared for the future and foster long-term environmental stewardship. Through the African Wildlife Foundation you can give to the Manyara Ranch Primary School and through the David Sheldrick Wildlife Trust you can indicate specific school supplies or experiences that you want to support. There are also a variety of ways that the money for donations can be raised.
Can I help without money? Absolutely. There are a variety of actions you can take right now that all contribute to elephant conservation or the conservation of other large herbivores:
- Talk to people about the ivory trade. Although the greatest demand for elephant ivory is in Asia, don’t forget how pervasive and influential Western culture is around the world- a continued, strong message that the loss of world elephant populations is not worth the ivory gained in return can help change attitudes.
- Remember that not all elephants live in parks and nature preserves. Elephants in zoos and other establishments need just as much support- you can volunteer your time and energy to help make life out of the wild as enjoyable and engaging as possible. There are also elephant sanctuaries that need volunteers.
- Pay attention to the state of large herbivores in your area- where I live, moose populations are down this year and scientists aren’t quite sure why. In Michigan, the decrease in moose numbers on Isle Royale has meant volunteer opportunities for helping with the summer research. There are usually a range of volunteer positions with state and local wildlife officials, some of which involve habitat management or data collection- contact your Dept. of Fish & Wildlife to see how you can help.
Elephants are big animals with big conservation concerns- that seems to equal trouble². But there are specific steps that can be taken, even if we live on a different continent, to help them and the people around them. Halting the ivory trade will take time and effort, as will more accurate understanding and management of elephant ecosystem roles, but perhaps elephant conservation benefits from the very nature of its size- hopefully once it gets started, it just keeps going.
Works Cited:
Blignaut, J., de Wit, M., and J. Barnes. 2008. “The Economic Value of Elephants” In: R.J. Scholes and K.G. Mennell (eds.) Elephant Management: A Scientific Assessment of South Africa. Witwatersrand University Press, Johannesburg.
As I mentioned in my last post, researchers are still learning about the ways in which elephants, and other large herbivores, impact the environment around them. In many ways, the goal is to figure out how many elephants can fit into an area before their resource needs lead to environmental degradation. One way to do that is to exclude elephants from specific spots and then compare those spots with others that elephants can access. This is exactly what Lagendijk et al. (2012) did with sites in South Africa, although they added a little twist since nyalas, large antelopes, were also present in the area- they used one type of fence to exclude elephants and a separate type to exclude both elephants and nyalas. As it turned out, elephants weren’t the only animals altering vegetation- while plant communities stayed largely the same in areas that only smaller herbivores could reach, plant communities changed in the same ways when elephants and/or nyalas were present- when elephants were excluded, nyalas increased their browsing pressure.
“Elephant browses the trees at Inyati, Sabi Sands Game Preserve, Limpopo, South Africa”
Sometimes you’re trying to assess impact over a very large area or sometimes the animals you are working with don’t like hanging out with people, so you look for other options. Simms (2009) used satellite imagery to investigate vegetation changes in a private game reserve in South Africa (if any of you have heard of archaeologists finding Mayan cities by looking for patches of younger forest, it’s the same principle- although the green may all look the same to our eyes, at certain wavelengths, the light reflected by older forests is different from that reflected by younger forests). Once again, although elephants did damage and alter vegetation, fire and rain patterns were also very important, and Simms even suggested that the impact of the grazing community (zebra, wildebeest, etc.) within the reserve was of bigger concern.
Are there any surprises about elephant roles? There were quite a few moments when I thought, “Wow, that’s amazing and/or scary”- here’s a brief summary:
- In Kruger National Park, Kohi et al. (2011) found that elephant-damaged mopane trees had many more (30x!) green leaves and more leaves closer to the ground (easier access for smaller animals) than untouched trees
- Forest elephants in the Rep. of Congo moved 14% of the seeds they ingested more than 10 km from the parent plant (Blake et al. 2009)
- Although not a study directly on elephants, when researchers looked at which animals were dispersing which seeds in a park in Rwanda, they found that no one was really visiting Parinari excelsa trees (Gross-Camp et al. 2009)- in other places, elephants disperse those seeds, but there were no elephants in the studied park. Without dispersal agents, the researchers were concerned about the future of P. excelsa in the park. (for more info on similar studies, check out the Center for Tropical Ecology and Conservation)
- And (saving the best for last!), observations from a research in Sri Lanka (Campos-Arceiz 2009)suggest that, in addition to providing food and other resources for invertebrates, elephant dung provides habitat for amphibians (specifically frogs)- really?!
Photo by David Govtaski for USFWS Northeast Region
Do any other herbivores play similar roles in other places? Yes, and no. There are a variety of large herbivores that disperse seeds, impact plant communities through browsing pressure, create special habitats for other species, and so on, but no one else does it quite like elephants. Cristoffer & Peres (2003) feel that one of the reasons rain forests in the Americas differ so much from those in Africa and Asia is the lack of elephants- tapirs in the Americas are important for seed dispersal and they are big enough to be dangerous, but they are still much smaller than elephants. Outside of the tropics, moose, reindeer, and other browsers alter vegetation patterns and influence habitat. Moose in particular have received a lot of attention in terms of their environmental impact: their browsing tends to open up the canopy, creating more room for shrubs and herbs; because they are selective eaters, areas heavily influenced by moose tend to become more dominated by conifers; and their dung facilitates nutrient cycling (Persson et al. 2000). Like elephants, moose have an impact on their world simply through the steps they walk- based on Persson et al.(2000)’s formula and the estimate of 4500-5000 moose in New Hampshire, I calculated that each year moose here trample an area equivalent to Squam and Newfound Lakes, combined- not bad for animals that wander around at their own pace.
Disturbing the landscape or disappearing from it? This is the big issue with all of these large herbivores. As I have mentioned before, elephants are increasingly confined to parks with fences that limit seasonal movements and tend to concentrate their impact within specific areas- too many animals, and the environment starts to degrade; too few and grassland areas can start to close up again. In forested locations, many large-seeded plants depend upon large herbivores to disperse their seeds so that seedlings don’t compete with each other or cluster together where a fungus or plant-eater can take them all out at once. Without dispersers, forests begin to lose their biodiversity, as in the Central African Republic where a study found that sites with high levels of hunting had fewer plant species (Vanthomme et al. 2010). Moose in large numbers in Fennoscandia damage timber trees and change plant communities, but their actions also increase the number of dead and dying trees which other species need for survival (Edenius et al. 2002)- in NH moose numbers are down and white-tailed deer don’t interact with the environment in the same manner, so a declining moose population could be a big deal.
When you are a big animal, you generally need more food and tend to have a larger home range. You also tend to have a lot of influence on what happens in the ecosystem around you. As human use of the landscape expands around the globe, it’s becoming harder for populations of some large herbivores to find some level of stability, and loss of these animals would, like a rock thrown in a pond, have consequences that expand through the ecosystem. But there are ways to balance the needs of different species and the needs of human society and wildlife; there are also ways that each of us can contribute toward that balance. In my next post, I’ll look at why large herbivores are important to us for more than aesthetic or intrinsic reasons and what we can do to support both them and the people who live with them around the world.
Works cited:
Blake, S., Deem, S.L., Mossimbo, E., Maisels, F., and P. Walsh. 2009. Forest elephants: tree planters of the Congo. Biotropica 41(4): 459-468.
Campos-Arceiz, A. Shit happens (to be useful)! Use of elephant dung as habitat by amphibians. Biotropica 41(4): 406-407.
Cristoffer, C. and C.A. Peres. 2003. Elephants versus butterflies: the ecological role of large herbivores in the evolutionary history of two tropical worlds. Journal of Biogeography 30: 1357-1380.
Edenius, L., Bergman, M., Ericsson, G., and K. Danell. 2002. The role of moose as a disturbance factor in managed boreal forests. Silva Fennica 36(1): 57-67.
Gross-Camp, N.D., Mulindahabi, F., and B.A. Kaplin. 2009. Comparing the dispersal of large-seeded tree species by frugivore assemblages in tropical montane forest in Africa. Biotropica 41(4): 442-451.
Kohi, E.M., de Boer, W.F., Peel, M.J.S., Slotow, R., van der Waal, C., Heitkonig, I.M.A., Skidmore, A., and H.H.T. Prins. 2011. African elephants Loxodonta Africana amplify browse heterogeneity in African savanna. Biotropica 43(6): 711-721.
Lagendijk, G., Page, B.R., and R. Slotow. 2012. Short-term effects of single-species browsing release by different-sized herbivores on Sand Forest vegetation community, South Africa. Biotropica 44(1): 63-72.
Persson, I., Danell, K., and R. Bergstrom. 2000. Disturabce by large herbivores in boreal forests with special reference to moose. Annales Zoologici Fennici 37: 251-263.
Simms, C. 2009. The utilisation of satellite images for the detection of elephant induced vegetation change patterns. Masters thesis, University of South Africa.
Vanthomme, H., Belle, B., and P. Forget. 2010. Bushmeat hunting alters recruitment of large-seeded plant species in Central Africa. Biotropica 42(6): 672-679.
“Eastern Serengeti 2012 06 01”- Savanna elephants
I spent the last week looking through lots of documents on elephants (even a few theses, so there was a mountain of reading), and I’ve learned quite a bit about what elephants eat, how populations have changed, and the impact that these mega-herbivores can have on the environment around them- they definitely live on a large scale. Some of the big ideas I gleaned from my elephant reading are:
- These animals eat a lot of food, they pull off bark, and they even knock down trees (Coetzee et al. 1979), and their diet is very adaptable (Steyn 2003).
- Elephant ranges have become increasingly restricted, partly through conversion of land for agriculture and development, and partly because elephants are confined to specific areas (like parks) by fences (Cumming et al. 1997).
- When talking about elephants in Africa, it’s important to differentiate between savanna elephants (Loxodonta africana) and forest elephants (Loxodonta cyclotis)- they interact with their environment in diverse ways (Blake 2002).
Elephant populations around the world have fluctuated– for example the ranges of savanna elephants have contracted over 75% since AD 1500 (Morrison et al. 2007), and the elephant population of the Eastern Cape of South Africa had been nearly destroyed by 1931, but by 2001 there were over 400 animals (Boshoff et al. 2002). As a result of these changes in elephant ranges and numbers, we’re still figuring out how elephants fit into ecosystems. And since both elephants and some plants (such as trees) can live for a long time, it may be decades before we fully understand all the pieces of the puzzle- imagine trying to study the environmental impact of an animal that lives 60-70 years, especially when it has been reintroduced to a location in the last decade. We do know that elephants eat a wide variety of foods and that their food preferences may change from season to season, and elephants do more than just eat- they remove plants, make trails, and even create watering holes (Steyn 2003).
Forest elephants vs. savanna elephants. These two species can have very different effects on the world around them- both create paths between resources, but forest elephants eat more fruit while savanna elephants eat more grasses. Since only some trees are fruiting at a particular time (versus grass which is usually available over longer periods of time), it’s important to remember where they are at the right moment, and trails can help elephants in that regard- paths around fruit tree patches tend to be bigger (Blake & Inkamba-Nkulu 2004) perhaps as a way to lead elephants to those resources. These trails operate as highways for other species, giving them access to areas they may not otherwise have reached. Forest elephants also help disperse seeds from fruiting plants and can move them great distances. Why is this important? Apart from helping the plants spread to new locations (an estimated 3192 seeds/elephant/day!), some of the plants are used as economic resources by people (Dudley 2000).
By stripping bark off the trunk, elephants can injure or even kill the tree
Savanna elephants are involved in the transformation of woodland and thickets into grassland (although not the only factors and I saw many, many differing estimates of how important elephants are)- by pulling down trees and breaking tree trunks, they can open up areas for colonization by grass, which is helpful for some species such as zebra (Steyn 2003)- of course, that can be a problem for animals like giraffes which browse on woody vegetation (Chafota 1998). Why is this important? If you’re trying to manage a reserve or park, your decisions are made more complicated when a species both helps and harms others.
So why did I put elephants on a tight-rope? To a large degree, keeping elephants and ecosystems healthy seems to be about balance: balance between space and population density, and balance between competing interests. As a result of restrictions in movement caused by park fences plus growing populations, elephant densities in some areas have reached unnaturally high levels (Cumming et al. 1997)- those crowded elephants have no place to go and all depend on the same resources, which can lead to habitat degradation, as in Amboseli National Park where bushbuck and lesser kudu disappeared due to elephant-caused changes in the ecosystem. At the same time, too few elephants can have an equally negative impact on some species- in Hluhluwe Game Reserve, zebra and wildebeest declined after extermination of elephants helped forests and thickets spread (Chafota 1998). Transition from woodland to grassland is helpful for grazers, but not necessarily for browsers- how do you maintain enough of each habitat? Tourists want to see elephants- it’s easier to see find elephants when they exist at higher densities, but that could mean declines in other animals such as black rhinos. It’s all about finding the pivot point.
So there are many ways in which elephants interact with what is around them, and, in some cases, researchers are finding newer ways of measuring those interactions. The amount of disagreement about elephant impacts I found in this background reading surprised me, although I guess I should expect such a massive animal to be the subject of a wide range of opinions. For next week, I’m going to look at more current research and also take a peek at how these issues connect to large herbivores in other locations. There are so many facets to this topic and I don’t expect to touch upon them all- given the complex nature of elephant ecology, there may be no single lesson to take away from this, but I imagine that it’s going to be pretty fascinating no matter what I uncover in this information mega-transect.
Works Cited:
Blake, S. 2002. The ecology of forest elephant distribution and its implications for conservation. PhD dissertation, University of Edinburgh.
Blake, S. and C. Inkamba-Nkulu. 2004. Fruit, minerals, and forest elephant trails: do all roads lead to Rome? Biotropica 36(6): 392-401.
Boshoff, A., Skead, J., and G. Kerley. 2002. Elephants in the broader Eastern Cape- an historical overview. In Kerley, G., Wilson, S., and A. Massey, eds. “Elephant Conservation and Management in the Eastern Cape: Proceedings of a Workshop Held at the University of Port Elizabeth.” Terrestrial Ecology Research Unit: Port Elizabeth, South Africa.
Chafota, J. 1998. Effects of changes in elephant densities on the environment and other species- how much do we know? From “Proceedings from the Workshop on Cooperative Regional Wildlife Managements in Southern Africa” University of California, Davis, August 13-14, 1998.
Coetzee, B.J.,Engelbrecht, A.H., Joubert, C.J., and P.F. Retief. 1979. Elephant impact on Sclerocarya caffra trees in Acacia nigrescens tropical plains thornveld of the Kruger National Park. Koedoe 22: 39-60.
Cumming, D.H.M, Fenton, M.B., Rautenbach, I.L., Taylor, R.D., Cumming G.S., Cumming, M.S., Dunlop, J.M., Ford, G.S., Hovorka, M.D., Johnston, D.S., Kalcounis, M.C., Mahlanga, Z., and C.V. Portfors. 1997. Elephants, woodlands and biodiversity in miombo woodland in southern Africa. South African Journal of Science 93: 231-236.
Dudley, J.P. 2000. Seed dispersal by elephants in semiarid woodland habitats of Hwange National Park, Zimbabwe. Biotropica 32(3): 556-561.
Morrison, J.C., Sechrest, W., Dinerstein, E., WIlcove, D.S., and J.F. Lamoreux. 2007. Persistence of large mammal faunas as indicators of global human impacts. Journal of Mammalogy 88(6): 1363-1380.
Steyn, A. 2003. The impact of introduced elephant on selected woody plant species on the Songimvelo Game Reserve. Dissertation, Technikon Pretoria.
Anyone who has seen the most recent issue of National Geographic will understand why I chose this topic. The cover article looked at the resurgence in poaching for the ivory trade, and the journalist talked to a wide variety of people involved in the illegal trade to provide an understanding of what is driving demand. I found it depressing to learn that poaching of elephants was on the rise again- I thought we had been making progress there.
I find it very worrying that demand for ivory continues to put elephants at risk- if we can’t protect animals as charismatic as elephants from poaching, how we possibly be effective in protecting less popular animals? And I do realize the economic element of poaching- if you had to choose between feeding your family and saving a wild animal, which would you choose? But there must be a way to keep elephants from becoming extinct in the wild because of human hunger for ivory.
This got me thinking about what might happen if elephants are poached to extinction in an area- aside from losing income, how would that impact the poachers’ lives? Would there be changes to the environment around them? So this month I’m going to investigate the ecological roles of large herbivores, particularly elephants, to better understand what an elephant-less ecosystem might be like. I have heard that elephants alter landscapes by pulling up trees, and I’m sure that they have other impacts as well. Maybe protecting elephants can also be about protecting livelihoods.
I’m not going to provide a history of the ivory trade and poaching, partly because it would depress me quite a bit and partly because I imagine that you already have some background knowledge there. Instead I’m going to focus on how elephants alter and/or maintain their environment, and how that impacts human society. I’d also like to expand some of my search to other large herbivores- we may not all live near elephants, but there may be other animals in our backyards that fill similar roles. If there is an aspect of elephant ecological roles that is interesting to you, send me an e-mail and I’ll see what I can dig up.
So stay tuned as I explore what a several-ton animal does with its time.
