As I have mentioned before, habitat fragmentation is one of the primary issues facing species around the world today- while it is far too big a topic to tackle in its entirety during one month’s posts, I think that investigating a few of its manifestations is manageable. I also think it’s necessary, since we have degrees of control over some causes of fragmentation and options that species have for responding to these changes in their habitat. I want to keep this discussion focused on small-scale, local habitat fragmentation- things like roads and fields and dams- because we can see these all around us, but we may not be thinking about their larger effects on the ecosystems around us.
Hedgehogs are used to dealing with a variety of ground surfaces, but they seem to move more quickly when they encounter artificial surfaces like asphalt
So let’s start with deliberate construction, the things we intentionally build. Roads are certainly one of the biggest barriers to animal movement, and there are a few reasons for this. For some animals, the physical road itself is undesirable habitat, especially when constructed from asphalt; hedgehogs in the UK, for example, were found to use a different type of running locomotion when sprinting across roads than when moving quickly through vegetation (Rondinini & Doncaster 2002), and they largely avoided crossing roads when possible. For other animals, there appears to be a psychological reluctance to approach roads, either because it means exposure to predators or because it means nearing human activity. When several bird species in Scotland were lured toward gaps between forest fragments using bird calls, goldcrests were largely unwilling to venture into open areas, possibly because their smaller wings and slower flight made them more vulnerable to predation (Creegan & Osborne 2005).Likewise, reindeer in Norway stayed several kilometers away from roads, power lines, and an associated tourist resort even though that meant loss of better foraging habitat (Vistnes & Nellemann 2001)- since this behavior was particularly marked in females during calving, this could lead to both overgrazing of used habitat and reduced survival of females and young. And then there is the most readily seen impact of roads: mortality. When looking at painted turtle populations in southern NH, Marchand (2002) found that ponds with many nearby roads had more adult and male turtles- females have to leave the ponds to find suitable nesting sites, leaving them vulnerable to traffic if they have to cross roads, and, if they are reluctant to cross, instead nesting closer to other females than they would normally, the eggs and juveniles are more likely to be found and eaten by predators- it’s kind of a no-win situation.
He was not a happy camper about being measured, and he’s probably a bit grumpy about being stuck above the dam
And let’s remember that we don’t just alter terrestrial systems. When I was working with wood turtles in southern NH, we found two very old, rather cranky males along the Ashuelot River in Surry- we estimated their age to be around 70 (which is pretty fantastic!)- unfortunately, we found no females in the area and no younger males. Although we knew of other sections of the river with wood turtle populations down river, the prognosis for these guys ever finding a mate was pretty grim because of a dam directly downstream from them (since the dam was built in 1941, these guys would have been just a few years old when construction stranded them upsteam). Even when access points are provided in dams and bridges, it may still prevent adequate movement between areas- brook charr densities in Quebec were much higher below highway crossings than above them (Pepino et al. 2012), and culverts placed over road crossings in Michigan channeled stream flow so much that crayfish had difficulty moving through them (Foster & Keller 2011). Why should we care about this? Well, to start with, as of 2011, the United States had 4,094,447 miles of roads (www.fhwa.dot.gov/policyinformation/statistics/2011). Between 1937 and 1999, road density in northern Wisconsin increased by more than 100% (Hawbaker et al. 2006)- imagine being a longer-lived animal in this landscape: the world you know is continuously more fragmented. Reduced movement between areas means reduced genetic variation which can lead to decreased resistance to further changes and threats- bobcat populations bordering roads in southern California showed lowered genetic diversity (Ruell et al. 2012). It also means that, if some event causes one population to disappear, the odds that the area will be recolonized by members of another population are low- ground beetles in Switzerland did not move between areas on either side of a road (Keller & Largiader 2003); this is very small-scale, and yet incredibly powerful, isolation.
The structures we create to facilitate trade, generate energy, control water flow, etc. have immediate impacts on the ecosystems that surround them. By disrupting movement of animals between locations, we can trap populations, reduce genetic diversity, and effectively sentence groups to extirpation. And there are definitely ways that we fragment species without turning soil into asphalt or building a wall too high to scale- for my next post, I’ll look at other types of small-scale fragmentation, including indirect effects of our lifestyles.
Works cited:
Creegan, H.P. and P.E. Osborne. 2005. Gap-crossing decisions of woodland songbirds in Scotland: and experimental approach. Journal of Applied Ecology 42: 678-687.
Foster, H.R. and T.A. Keller. 2011. Flow in culverts as a potential mechanism of stream fragmentation for native and nonindigenous crayfish species. Journal of the North American Benthological Society 30: 1129-1137.
Hawbaker, T.J., Radeloff, V.C., Clayton, M.K., Hammer, R.B. and C.E. Gonzalez-Abraham. 2006. Road development, housing growth, and landscape fragmentation in northern Wisconsin: 1937-1999. Ecological Applications 16: 1222-1237.
Keller, I. and C.R. Largiader. 2003. Recent habitat fragmentation caused by major roads leads to reduction of gene flow and loss of genetic variability in ground beetles. Proceedings: Biological Sciences 270: 417-423.
Marchand, M.N. 2002. Effects of landscape composition on rates of nest predation and population structure of painted turtles in southeastern New Hampshire. M.S. thesis, University of New Hampshire, Durham.
Pepino, M., Rodriguez, M.A. and P. Magnan. 2012. Impacts of highway crossings on density of brook charr in streams. Journal of Applied Ecology 49: 395-403.
Rondinini, C. and C.P. Doncaster. 2002. Roads as barriers to movement for hedgehogs. Functional Ecology 16: 504-509.
Ruell, E.W., Riley, S.P.D., Douglas, M.R., Antolin, M.F., Pollinger, J.R., Tracey, J.A., Lyren, L.M., Boydston, E.E., Fisher, R.N. and K.R. Crooks. 2012. Urban habitat fragmentation and genetic population structure of bobcats in coastal southern California. American Midland Naturalist 168: 265-280.
Vistnes, I. and C. Nellemann. 2001. Avoidance of cabins, roads, and power lines by reindeer during calving. The Journal of Wildlife Management 65: 915-925.
This month I’ll be focusing on one part of a very big issue- habitat fragmentation, in all of its forms, is a huge problem for species around the world and the ecosystem services they provide. Some species require a certain amount of territory for their home ranges, and habitat fragmentation may leave them unable to meet their needs in the space they have. Other species need a certain type of habitat, for example the vegetation deep within forests, and cutting up the forest into smaller blocks reduces the amount of deep forest, leaving them to make do with less favorable areas.
It’s an interesting patchwork of habitats to look at and a challenge for dispersal
And sometimes the fragmentation issue has to do with finding new territory or others of your species– if you’re a juvenile animal ready to strike out on your own, what happens when you have to cross human-dominated landscapes to reach the next patch of suitable habitat? It’s hard enough to learn the dangers and resources of a new place (think of all of those freshmen who started college this fall…), but adding roads to cross and neighborhoods to go around makes the process even more difficult. The challenges can be just as great if you are an adult male looking for a mate- getting to where potential partners are could be more than half of the challenge (and after all of your efforts, you may still have to impress her). This is the type of habitat fragmentation I’ll be looking at in my posts this month- the barriers to movement that are created on local (and larger) levels by changes in the environment, many of which are the result of human activity.
And I’ll be bringing in my field experiences relating to this issue- I have been both saddened by the isolation of some animals I’ve worked with and amazed by the obstacles that others have overcome. So stick with me as I trace the impact of habitat fragmentation on animal dispersal (at the very least, I have some good pictures…).
Over the past few posts, hopefully you have gotten a sense of how a combination of increasing demand and general prejudice has led to massive overexploitation of shark populations around the world- some of the information I have passed along is pretty bleak. But I don’t want you to think that it’s all doom and gloom for sharks- new protection and management measures in diverse locations have started to turn things around for some populations, so we know that taking action now can still be effective. But it’s going to take concerted effort on the part of many to reverse shark declines, and that’s where you come in.
Things you can do to help sharks:
- Choose shark-friendly products– remember that thousands of sharks are caught each year as fishery by-catch, so look for the Marine Stewardship Council (MSC) label on fish you purchase- certified fisheries are using recommended best practices, and that can make a big difference for sharks. And think about the products you use which might come from sharks- a little investigation before purchase could be important. Chondroitin sulfate used in supplements, for example, usually comes from domestic livestock, but sharks have also been used as a source, so check the labels for ingredients
- Adopt a Shark– there are a number of programs that allow you to sponsor a specific species and contribute to conservation efforts- check out
o South African White Shark Research Institute
o National Wildlife Federation (you can also adopt rays!)
o World Wildlife Fund
- Help scientists keep track of whale sharks– if you happen to have vacation pictures from a whale shark encounter (oh, to be so lucky!), you can submit them to the ECOCEAN Whale Shark Photo-identification Library– since the spotting on whale sharks is unique among individuals, scientists can ID your shark from the picture and they will even let you know when it is seen again
- Volunteer for shark organizations and shark research:
o Coral Reef Alliance in California appreciates volunteer help at specific events and over the long term
o Australian Marine Conservation Society needs volunteers in their Brisbane office, at special events, and who can do things like data entry and organization from home
o The Shark Trust uses volunteers in-house, at educational events, and to create content for their website- they also coordinate a yearly ‘Great Eggcase Hunt’ along the beaches of the UK to help provide scientists with data on reproductive rates (I love this idea!)
o Get into the water for research- both the Shark Conservation Society and the Thresher Shark Project have scientific expeditions that members can join, and EarthWatch has a project in Belize
- Take action as a citizen– be sure to inform your legislators about your support for shark conservation, and you can be alerted about general marine conservation issues and opportunities to join campaigns by the Ocean Conservancy
- Spread the word about shark conservation– you might live in the middle of a continent, far from beaches and reefs and open ocean, but the health of our marine systems impacts us all, so let people around you know about the pressures facing sharks
Sharks have traditionally been feared and persecuted, with the result that populations around the world have plummeted. We can help sharks recover and maintain their ecological roles in marine systems, but this needs to be a global, sustained effort- I hope that you are inspired to put in a good word for sharks and contribute to their conservation.
My last post presented a pretty bleak view of current shark populations and the challenges they face, so this week I want to focus on the ways that researchers are trying to understand the most important aspects of shark conservation- sometimes the strategies they propose aren’t effective, but still lead to improved shark knowledge and protection.
Great Hammerhead Shark
One option is to protect the areas which are important to specific populations that are in trouble. Nursery areas, for example, have been suggested as great targets for conservation (Heupel et al. 2007)- although definitions for what a nursery is are still evolving, the general idea here is places where females give birth or lay eggs, or places where juveniles grow toward maturity. It is possible that these areas have high food density or low predator density (remember that little sharks are eaten by bigger sharks), or it could be that the warmers water usually associated with nursery areas allows sharks to grow more quickly. We do have to be careful, however, about focusing too much on nursery areas alone- when school shark nursery areas were protected in Australia, but harvesting of adults continued, populations still declined because the juveniles weren’t growing quickly enough to reach breeding maturity and replace the lost adults (Kinney & Simpfendorfer 2009). Certain areas of the world seem more important for shark conservation than others. Coastal sharks are particularly at risk because of proximity to human activity (Speed et al. 2010), and Pacific coastal sharks at the mid-latitudes (read: around southern Japan and Australia) show the highest species richness of sharks anywhere, making these areas very important for conservation of shark biodiversity (Lucifora et al. 2011). Time of year and even time of day make things even more complicated. Most species of shark are known to show some type of migratory pattern- recent research in South Africa, for example, showed that although male and female great whites were found together feeding on seals in the winter, during spring and summer months females stayed in inshore areas while males dispersed (Kock et al. 2013). Whale shark numbers off the coast of India increase during the pre-monsoon period and then the animals seem to leave the coast during the monsoon (Pravin 2000). Some shark species are more active at night, as with the blue shark in the eastern Atlantic- GPS tracking of these animals revealed that they had daily depth migration patterns, and night-time foraging in highly productive waters was concentrated in the top 100m of water, essentially the same depths targeted by long-lines fishing for swordfish and tuna, putting the sharks at risk (Queiroz et al. 2012).
Better-regulated and -ENFORCED international regulations have also been called for. Scientists studying shark populations off the coast of Italy have suggested that efforts to protect shark species there are hampered by lack of information on exactly which shark species are being caught (Dell’Apa et al. 2012), and I found that was a regular refrain, from IUCN reports (Camhi et al. 2009) to discussion of harvest numbers from Chile (Sebastian et al. 2008). Genetic tests can help keep track of species numbers, and several countries including the US have passed regulations requiring that fins must remain attached to sharks that are landed to reduce the practice of finning sharks and leaving them in the ocean to die and promote use of all parts of landed sharks (Techera 2012). One of the big issues with regard to shark conservation is enforcing regulations and developing international cooperation. Many international plans for shark protection provide guidelines for shark protection but lack the power to generate consequences for groups that ignore the guidelines (Techera & Klein 2011); since sharks are such mobile animals, this means that the efforts of one country with strong domestic protections can be totally undone by a neighbor without the same commitment. Some researchers have suggested that focusing on the difference in economic value between living and dead sharks may be one way to generate support for shark protection- it was estimated that a living shark which helped attract shark tourism to Palau was worth $1.9 million over its lifetime, versus $114 as a harvested animal (Techera 2012).
And these efforts are having an impact, albeit slowly. White shark numbers around Australia have increased as a result of protection (Ward-Paige et al. 2012); as a result of gillnet bans in the eastern Pacific, school shark numbers are up as well. Changes in fishery practices have also helped diamond and brown ray populations around South Africa and little and rosette skate populations in the northwest Atlantic. Several nations have created shark sanctuaries out of their territorial waters, including Palau, the Bamahas, Honduras, and the Maldives (Techera 2012).
So researchers are doing their best to understand what makes shark conservation effective, and groups around the world are working to create movements and legislation to make shark protection widespread- I have no doubt that researchers and activists could use our help in their efforts. In my final post for the month, I’ll provide ways that you can directly impact shark conservation without even going in the water (unless you want to…).
Works cited:
Camhi, MD, Valenti, SV, Fordham, SV, Fowler, SL, and C Gibson. 2009. The Conservation Status of Pelagic Sharks and Rays: Report of the IUCN Shark Specialist Group Pelagic Shark Red List Workshop. IUCN Species Survival Commission Shark Specialist Group. Newbury, UK.
Dell’Apa, A, Kimmel, DG and S Clo. 2012. Trends of fish and elasmobranch landings in Italy: associated management implications. ICES Journal of Marine Science 69: 1045-1052.
Heupel, MR, Carlson, JK, and CA Simpfendorfer. 2007. Shark nursery areas: concepts, definition, characterization and assumptions. Marine Ecology Progress Series 337: 287-297.
Kinney, MJ and CA Simpfendorfer. 2009. Reassessing the value of nursery areas to shark conservation and management. Conservation Letters 2: 53-60.
Kock, A, O’Riain, MJ, Mauff, K, Meyer, M, Kotze, D, and C Griffiths. 2013. Residency, habitat use and sexual segregation of white sharks, Carcharodon carcharias in False Bay, South Africa. PLoS ONE 8: e55048.
Lucifora, LO, Garcia, VB and B Worm. 2011. Global diversity hotspots and conservation priorities for sharks. PLoS ONE 6: e19356.
Pravin, P. 2000. Whale shark in the Indian coast- need for conservation. Current Science 79: 310-315.
Queiroz, N, Humphries, NE, Noble, LR, Santos, AM and DW Sims. 2012. Spatial dynamics and expanded vertical niche of blue sharks in oceanographic fronts reveal habitat targets for conservation. PLoS ONE 7: e32374.
Sebastian, H, Haye, PA and MS Shivji. 2008. Characterization of the pelagic shark-fin trade in north-central Chile by genetic identification and trader surveys. Journal of Fish Biology 73: 2293-2304.
Speed, CW, Field, IC, Meekan, MG and CJA Bradshaw. 2010. Complexities of coastal shark movements and their implications for management. Marine Ecology Progress Series 408: 275-293.
Techera, EJ. 2012. Fishing, finning and tourism: trends in Pacific shark conservation and management. The International Journal of Marine and Coastal Law 27: 597-621.
Techera, EJ and N Klein. 2011. Fragmented governance: reconciling legal strategies for shark conservation and management. Marine Policy 35: 73-78.
Ward-Paige, CA, Keith, DM, Worm, B and HK Lotze. 2012. Recovery potential and conservation options for elasmobranchs. Journal of Fish Biology 80: 1844-1869.
When I sat down to read about shark declines around the world, I had thought I was prepared for the numbers I was about to encounter: it’s very bad, we know this now, time to reserve the trend. But as I became more and more depressed about the current situation of shark species, I realized I hadn’t before recognized either the magnitude of the problem or how long we’ve had an inkling it was occurring. And that makes me feel like we’ve dropped the ball on this one, although it’s probably par for the course when we consider our general treatment of the world’s oceans.
Great Hammerhead Shark
What types of declines are we talking about? Well, it feels a little crazy to realize that I am not throwing out these numbers in an attempt at exaggeration, but it looks very, very bad. Let’s start with some of the rosier views: a 2004 assessment of shark species in the Mediterranean suggested that about 46% of sharks and their relatives were threatened, although not enough data were available on another 30% (Abdulla 2004); Baum et al. (2003) suggested that tiger sharks in the northwestern Atlantic had declined by 65% between 1986 and 2000 and that the average decline in shark species they had investigated was over 75% during that time. The numbers only get scarier from here: hammerheads in the northwestern Atlantic declined by 89% between 1986 and 2000 (Baum et al. 2003); semi-pelagic hammerheads around the world have declined 64-99% overall (Camhi et al. 2009). Of the 20 species of large predatory sharks in the Mediterranean, Ferretti et al. (2008) could only find enough abundance data to analyze trends for 5 species- over the last 200 years, all 5 saw declines of over 96%. 96-99% over 200 years sounds horrible- but it actually pales in comparison to the plight of oceanic whitetip sharks in the Gulf of Mexico- that population declined by more than 99% between the 1950s and the 1990s (Baum & Myers 2004). When we consider that Gulf of Mexico whitetips were probably down from their historical numbers by the 1950s, we’re talking about less than 1% of the population left. And I have to admit that I’m a little annoyed that we let things get this bad before taking broadscale action- in 1991, South Africa had already recognized population declines in great whites and implemented protection of the species, and California followed suit in 1993 (Heneman & Glazer 1996), but the US didn’t act to ban finning of shark species until 2000 (Cunningham-Day 2002). Governments such as the US and Australia are still working to get global consensus and cooperation for shark conservation (more on that in a future post). It seems like we could have done more and done it earlier.
Why are shark populations declining so much? I think we can look at this one on two levels: the actions removing sharks directly from the oceans, and then the circumstances keeping populations from recovering. Sharks are killed on a massive scale. Some of that is unintentional, for example when they get caught in fishing nets or on long-lines set out for other species- according to Camhi et al. (2009), 28% of the fish caught on long-lines set out for migratory species are discarded, and blue sharks make up the largest portion of that discard. Some sharks are intentionally targeted to supply several industries: sharks are now caught for their fins (for soup), their livers (medicinal practices), their meat (food), their cartilage (medicinal uses), and for the sport of catching a shark. They also get caught in nets set up at beaches to protect bathers. Taken all together, the numbers are a bit staggering- in 2002, it was estimated that about 3000 sharks were killed in drift gill nets per day (Cunningham-Day 2002); Clarke et al. (2006) estimated that 10.7 million blue sharks were captured each year for the fin trade alone! Why can’t populations sustain this level of harvest? There are a few reasons for this. Habitat loss, that perennial conservation issue, contributes to shark issues, for example in areas where juvenile sharks congregate (sometimes called “nurseries”). Many species of shark are slow to mature and have low reproductive rates- the dusky shark, for example, requires roughly 2 decades to reach maturity. If a species is experiencing heavy fishing pressure, juveniles may not live long enough to reproduce. Some species segregate by gender except for breeding, for example females staying near the coast, and so shark fishing which concentrates in specific locations may create gender biases in the population (Hueter 1998)- there may be females who can’t find males or vice versa. When you put these issues together, it can take a very, very long time for shark populations to recover from being decimated- basking sharks off the coast of Ireland have yet to fully recover after more than 50 years of protection (Cahmi et al. 2009).
Why should we care about losing these fearsome animals? I could certainly make the argument that biodiversity in and of itself is a good thing, because it makes the world a more fascinating place. Or I could suggest that complex ecological systems are better able to withstand change, which will probably be helpful given the current and future impact of global climate change. I think that those are both very important reasons, but sometimes people need a more immediate reason to protect species, so think about what happens when the top predator is removed from a system- things can get a little crazy in what is known as a ‘trophic cascade’- smaller predators might suddenly become overly abundant because they are now at the top of the chain, prey populations can expand until they exhaust their food base, etc. (If you want to get a sense of the implications of trophic cascades in a variety of habitats, I suggest looking into sea otter-sea urchin dynamics along the Pacific coast, and mule deer-cougar/elk-wolf dynamics in national parks.) To give you a sense of how sharks allow us to continue harvesting certain resources, the decline of large sharks in the northwestern Atlantic has been linked to the collapse of the bay scallop fishery (Baum et al. 2003).
So sharks are clearly in trouble for a number of reasons, although overharvesting does stand out as a glaring issue. Over the past decade or so, researchers have really concentrated on exploring options for shark conservation- for my next post, I’ll dive into the strategies than have been proposed and implemented to support shark populations. We’ve done a pretty good job of destroying shark populations- hopefully we will be just as good at helping them recover.
Works cited:
Abdulla, A. 2004. Status and Conservation of Sharks in the Mediterranean Sea. IUCN Technical Paper. Pgs. 7.
Baum, JK and RA Myers. 2004. Shifting baselines and the decline of pelagic sharks in the Gulf of Mexico. Ecology Letters 7: 135-145.
Baum, JK, Myers, RA, Kehler, DG, Worm, B, Harley, SJ, and PA Doherty. 2003. Collapse and conservation of shark populations in the northwest Atlantic. Science 299 (5605): 389.
Camhi, MD, Valenti, SV, Fordham, SV, Fowler, SL, and C Gibson. 2009. The Conservation Status of Pelagic Sharks and Rays: Report of the IUCN Shark Specialist Group Pelagic Shark Red List Workshop. IUCN Species Survival Commission Shark Specialist Group. Newbury, UK.
Clarke, SC, McAllister, MK, Milner-Gulland, EJ, Kirkwood, GP, Michielsens, CGJ, Agnew, DJ, Pikitch, EK, Nakano, H, and MS Shivji. 2006. Global estimates of shark catches using trade records from commercial markets. Ecology Letters 9: 1115-1126.
Cunningham-Day, R. 2002. Sharks in danger. Biologist 49: 118-122.
Ferretti, F, Myers, RA, Serena, F, and HK Lotze. 2008. Loss of large predatory sharks from the Mediterranean Sea. Conservation Biology 22: 952-964.
Heneman, B and M Glazer. 1996. More Rare Than Dangerous: A Case Study of White Shark Conservation in California. Pp. 481-491. In: AP Klimley & DG Ainley (ed.) Great White Sharks: The Biology of Carcharodon carcharias, Academic Press, San Diego.
Hueter, RE. 1998. Philopatry, natal homing and localized stock depletion in sharks. Shark News 12: 1-2.
Maybe I was inspired by the Discovery Channel last month, or maybe it’s due to how many I see when I’m on the Louisiana coast doing field work, but this month I’ve decided to look more closely at the plight of sharks in the world’s oceans (and maybe this is just an attempt to face some primal fear I have…).
I know there are issues with regard to harvesting sharks for shark-fin soup, and I think there has been general persecution of sharks, in the same way that large terrestrial carnivores have been targeted because of the threat and competition they represent, but I feel like there must be more to the story than that. Given the kind of global population declines I’ve heard mentioned (reaching as high as 90%, which is pretty hard to ignore), I feel there must be other threats facing these animals, although maybe not- maybe we are doing a pretty thorough job of removing them from the oceans just through fear and appetite.
Atlantic sharpnose shark, one of the species common near the coast
I spend a lot of time on barrier islands in Louisiana during the spring and summer for field work, and, the majority of the time, getting onto an island means walking through the murky water from where we’ve anchored the boat. Although I rarely see creatures in the water for most of that walk, I am always thinking about what the possibilities are (and when I see small fish jump out of the water around me, seemingly in an attempt to escape from something, it doesn’t make me feel any better). I do regularly see small sharks of a foot or two in length hanging out right next to the shore, so I know they are there (and the one time I saw considerably bigger sharks, I really wished I hadn’t noticed…) and I assume they are feeding on fish and perhaps crustaceans in the area. What I don’t know (among other things) is whether the numbers and sizes of sharks I’m seeing are historically average- how bad have declines been along the northern coast of the Gulf of Mexico? And how do changes in Atlantic populations compare with things happening in the Pacific? And, although staying from shark-fin soup, do I still have a role in the forces decimating shark populations?
So, although it’s a little scary (and I will admit that I probably wouldn’t cover this topic in May or June, but now that I’m beached for a while, I think I can handle it), I’ll be focusing on shark research and conservation this month, hoping to shed a little light on the condition of these predators just beneath the surface.
Over the past few weeks, I’ve spent some time looking into firefly research and conservation around the world- some aspects of it were 
considerably more challenging to dig up than others, but I think that I have a much better sense of what it means to be a firefly and the roles that these insects play in our lives, both in the ecosystems around us and elsewhere. I’ve also learned about types of habitat change and pollution that we might not think of immediately- fireflies live in a challenging world and we’ve made it even more challenging for them through our actions
But there are definitely some things that we can do to help fireflies (and I have no doubt that quite a few of these would be good for other insects that we enjoy having around us, such as butterflies and honey bees), and, given the possibilities out there, you can choose your own adventure:
Want to learn more about fireflies in general, both near and far?
- There is an on-line journal specifically devoted to fireflies- check out Lampyrid– some articles you have to pay for, but others are open-access.
- There’s a researcher in Malaysia working very hard to educate people about the amazing synchronized flashers in that area- check out the blog.
Looking to make your yard, town, or city more fire-fly friendly?
- Firefly.org has suggestions for changes in your immediate environment, as well as small actions that can really add up across an entire region.
- A few years ago, the city of Kitakyushu in Japan made a concerted effort to bring back the fireflies which had once been a regular feature of their landscape- their work might inspire the community where you live.
Hoping to get up close and personal with fireflies?
- If you are in South Carolina, the Clemson Firefly Project wants data from your backyard.
- Across the eastern US, the Boston Museum of Science is collecting data from backyard firefly enthusiasts through their Firefly Watch– head outside on a weekly basis, record the fireflies you see, and then submit the data. And if you’ve always dreamed of analyzing scientific data, they are looking for your help as well!
And for those of you who are long-term planners and will settle for nothing but quality time with experts, the International Firefly Symposium will be held August 11-15, 2014 in Gainesville, FL.
It’s true that the summer season will be coming to a close in a few weeks, but you can still enjoy this year’s fireflies and start planning for how to help next year’s- and I’m sure that there are more options out there if the suggestions above don’t appeal to you. We can all work together to ensure that fireflies have a naturally bright future.
In my last post, I mentioned some of the challenges facing firefly populations around the world, including habitat loss and pollution, and this week I wanted to get a better sense of our options for halting population declines and making a human-dominated landscape more firefly-friendly. To be honest, I was kind of hoping to find a bit more than I found on conservation efforts (when you consider that the first recorded firefly protection plan dates to 1835 in Spain (Pyle 1995), I had assumed that quite a variety of strategies had been tried since then), but at least there are some ideas on where to start and important issues to consider as we move forward.
What are some general strategies to help firefly populations? Certainly, habitat restoration is a good place to start. When abandoned rice paddies in Kanazawa, Japan were restored, Luciola lateralis firefly populations doubled over four years (Koji et al. 2012). Researchers in Malaysia noted that the loss of specific trees along rivers decreased firefly reproductive success and recommended an ecosystem-wide approach to firefly conservation because fireflies depend on so many elements within any habitat (Jusoh et al. 2009/2010). This means looking not just at the presence of specific prey or plant species, but also watershed dynamics, pollution levels, dispersal potential, etc. Dealing with the light pollution issue is also key. As I mentioned before, bright lights inhibit flashing, and a study in Switzerland found that males were not attracted to females positioned under street lights, and females did not actively seek darker areas (Ineicher & Ruttimann 2012), so if the street lights cover the entire area occupied by females, the males will not find them. This suggests two strategies: 1) design street lights so that light is focused onto the hard surfaces, such as streets and parking lots, that they are meant to illuminate and away from vegetative areas utilized by fireflies; and 2) since many species of fireflies have specific times of night when they are most active, consider reducing artificial light during those few hours. The type of light emitted is also important- Hagen & Viviani (2009) found that fireflies in Brazil were sensitive to not only light intensity but also color, so using outside lights which fall within a different range of the spectrum could help alleviate negative impacts on firefly populations. Ecotourism may be a way to preserve firefly habitat in areas with synchronized flashers- interviews with local residents of a firefly gathering area in Thailand found that the level of involvement in firefly conservation was directly related to level of involvement in firefly ecotourism; however, there is a danger of environmental damage when ecotourism activities are highly popular and/or unregulated, and Chaikaew (2005) recommended better communication and education efforts, as well as the development of daytime activities so that local firefly populations are not over-exploited.
What about augmenting firefly populations? So far, although researchers are still learning about this option, there appear to be a few problems. Attempts to rear fireflies in captivity have not met with unqualified success– keeping large numbers of larvae together led to unequal growth in individuals, the spread of disease, and high mortality rates, and, while separating larvae did have greater success (35 of 80 individuals completed their lifecycle), the success rate was still below 50% (Ho et al. 2010) and individual rearing of fireflies may not be feasible on the scale needed to supplement wild populations. And the obstacles to captive breeding and rearing have expanded importance because of our use of luciferase in medical research- wild fireflies are harvested in the US to obtain the chemical. In one county in Tennessee alone, ~40,000 males were harvested in 2008, despite the fact that a synthetic alternative exists, and researchers believe that this level of harvest pressure is unsustainable in the long term (Bauer et al. 2013). Collecting fireflies from healthy wild populations and transferring them to other locations may not work, either. In Japan Luciola cruciata fireflies which had been moved from one location to another to supplement the local population had different flash rates from the local L. cruciata fireflies, and the different in flash patterns may have caused reproductive isolation of the native insects while the introduced insects met with reproductive success (Iguchi 2009). This suggests that adding to local populations may not be the solution it might seem even when the species are the same.
The ideas I discuss above are very much big-picture perspectives; there isn’t a huge amount of detail about the things that we can do as individuals, in our own small spaces, to support fireflies. For my final post of the month, I’ll investigate smaller-scale actions which can add up to big gains for fireflies.
Works cited:
Bauer, CM, Nachman, G, Lewis, SM, Faust, LF, and JM Reed. 2013. Modeling effects of harvest on firefly persistence. Ecological Modelling 256: 43-52.
Chaikaew, P. 2005. Local people participation in firefly ecotourism management: a case study in Ban Samaechai, Petchaburi Province. Master’s thesis, Mahidol University, Thailand: 1-3.
Hagen, O and VR Viviani. 2009. Investigation of the artificial night lighting influence in firefly (Coleoptera: Pampyridae) occurrence in the urban areas of Campinas and Sorocaba municipalities. Anais do IX Congresso de Ecologia do Brasil : 1-2.
Ho, J-Z, Chiang, P-H, Wu, C-H, and P-S Yang. 2010. Lifecycle of the aquatic firefly Luciola ficta (Coleoptera: Lampyridae). Journal of Asia-Pacific Entomology 13: 189-196.
Iguchi, Y. 2009. The ecological impact of an introduced population on a native population in the firefly Luciola cruciata (Coleoptera: Lampyridae). Biodiversity and Conservation 18: 2119-2126.
Ineicher, S and B Ruttimann. 2012. Impact of artificial light on the distribution of the common European glow-worm, Lampyris noctiluca (Coleoptera: Lampyridae). Lampyrid 2.
Jusoh, WFAW, Hashim, NR, and ZZ Ibrahim. 2009/2010. Distribution, abundance and habitat characteristics of congregating fireflies (Luciolinae: Lampyridae) in Rembau-Linggi Estuary, peninsular Malaysia. In Proceedings of Postgraduate Qolloquium Semester 1, Faculty of Environmental Studies, Universiti Putra Malaysia: 331-336.
Koji, S, Nakamura, A, and K Nakamura. 2012. Demography of the Heike firefly Luciola lateralis (Coleoptera: Lampyridae), a representative species of Japan’s traditional agricultural landscape. Journal of Insect Conservation 16: 819-827
Pyle, RM. 1995. A history of Lepidoptera conservation, with special reference to its Remington debt. Journal of the Lepidopterists’ Society 49: 397-411.
My foray into firefly ecology over the past week has been fascinating on a number of levels- clearly in my previous ideas about fireflies, I had far too simple a concept of what these insects were: fireflies are more diverse, more widespread, and more sophisticated than I had ever imagined. They are also more indicative of environmental conditions. Although I was thinking too narrowly about what it means to be a firefly, unfortunately I was not missing the big picture when it comes to concerns over firefly conservation- populations are declining worldwide for a number of reasons.
What does it mean to be a firefly? As it turns out, it doesn’t necessarily mean that you turn into a flying, glowing insect. While all firefly larvae are bioluminescent, not all adults are (Smith 2009)- witness Pyropyga nigricans which is found throughout North America, is active during the day, and uses pheromones rather than light to attract mates (Lloyd 1999) (and after I saw pictures of this species which ranges throughout New England, I wondered how many times I had brushed this beetle off me with a lack of respect because I didn’t know what it was). The firefly’s glow is caused by chemical reactions involving the enzyme luciferase, and production of nitrous oxide appears to act like a lightswitch and give the insect control over light production (Lewis & Cratsley 2008). Some firefly larvae go through an aquatic stage (such as Luciola ficta in Taiwan) while others (like Photuris pennsylvanica in eastern North America) inhabit soil. For those fireflies that do flash, in some parts of southeast Asia, males gather together in trees for synchronized flashing, which I think must be an amazing sight (and I did read a discussion of whether some species in North America do this as well- see Milius 1999). What are the common denominators? As I said before, all larvae are bioluminescent. And firefly larvae are predaceous- depending on where they are, they eat snails, slugs, earthworms, and other soft-bodied insects (Keiper & Solomon 1972, Ho et al. 2010). People all over the world are fascinated by fireflies (a large amount of the research I found was centered around how the light is produced, what types of signals are used, and how we can use luciferase in areas such as medicine- it seems to me that we are putting a lot of effort into understanding how fireflies do what they do, and not so much into whether they will be able to continue doing it in the future). Fireflies, wherever they are, also have the capacity to act as ecological barometers because their life-cycles are dependent on water, soil, and atmospheric health.
What ecological threats do fireflies face? In some ways, fireflies face the same issues that are causing problems for species around the globe: habitat loss and pollution (not exactly new or glamorous, right?)- but there are also a few twists to this story. When we think of habitat loss, we tend to think of forests being cut down, swamps being drained, and grassland being developed, and those types of changes are important for firefly conservation, but there are also smaller disturbances that are causing big problems. For species with aquatic larval stages, being able to disperse through water systems and move between water and soil is crucial- consequently, changes in water flow and stream access can prevent larvae from evading predators and finding prey, and changes to the form of irrigation ditches, such as cementing, trap larvae on one side of the barrier (many species in Japan, for example, have declined in part because of cement in irrigation ditches- see Koji et al. 2012). Efforts to control Phragmites reeds (you remember them from the invasive aquatics discussion, right?) through burning may be partially responsible for the decline in Photuris salina populations in Delaware (Heckscher 2010). And we need to expand how we think about pollution as well. For species with aquatic larval stages, water pollution is a big problem (Heckscher 2010, Koji et al. 2012)- and remember that terrestrial species can be injured by water pollution because their prey is often impacted by water quality. Fireflies can also be killed by sprayed pesticides, especially since many of these species tend to spend their time near water (which can harbor mosquitoes) and fields (which may contain harvestable crops). In addition to these more commonly-discussed types of pollution, fireflies also have to contend with light pollution- at least since the first half of the 20th century, we’ve known that bright lights can interrupt firefly behavior and prevent flashing displays (Buck 1937). Many researchers today see a relationship between declining global firefly populations and the spread of artificial light into more and more natural habitat (Thancharoen et al. 2008)- if fireflies don’t flash or can’t see response flashes because of light pollution, populations in human-altered landscapes are going to be in trouble.
So there is more to fireflies and firefly conservation than I had originally suspected, and I’m sure that I haven’t even scratched the surface yet. Hopefully this post gives you a sense of firefly ecology and the larger threats facing populations around the world- for my next post, I’ll look into what research says about what might work (or not) to counter these threats.
Works cited:
Buck, JB. 1937. Studies of the firefly. I. The effects of light and other agents on flashing in Photinus pyralis, with special reference to periodicity and diurnal rhythm. Physiological Zoology 10: 45-58.
Heckscher, CM. 2010. Delaware Photuris fireflies (Coleoptera: Lampyridae): new state records, conservation status, and habitat associations. Entomological News 121: 498-505.
Ho, J-Z, Chiang, P-H, Wu, C-H, and P-S Yang. 2010. Life cycle of the aquatic firefly Luciola ficta (Coleoptera: Lampyridae). Journal of Asia-Pacific Entomology 13: 189-196.
Keiper, RR & LM Solomon. 1972. Ecology and yearly cycle of the firefly Photuris pennsylvanica (Coleoptera: Lampyridae). Journal of the New York Entomological Society 80: 43-47.
Koji, S, Nakamura, A, and K Nakamura. 2012. Demography of the Heike firefly Luciola lateralis (Coleoptera: Lampyridae), a representative species of Japan’s traditional agricultural landscape. Journal of Insect Conservation 16: 819-827.
Lewis, SM & CK Cratsley. 2008. Flash signal evolution, mate choice, and predation in fireflies. Annual Review of Entomology 53: 293-321.
Lloyd, JE. 1999. On research and entomological education III: firefly brachyptery and wing “polymorphism” at Pitkin Marsh and watery retreats near summer camps (Coleoptera: Lampyridae; Pyropyga). Florida Entomologist 82: 165-179.
Milius, S. 1999.U.S. fireflies flashing in unison. Science News 155: 168-170.
Smith, BW. 2009. Firefly diversity in Columbia: patterns across a dynamic landscape. Master’s thesis, University of Florida.
Thancharoen, A, Branham, MA, and JE Lloyd. 2008. Building twilight “light sensors” to study the effects of light pollution on fireflies. The American Biology Teacher February: 6-12.
My appreciation for most insects was late in developing- I very much recognize their contributions to world ecosystems today and am aware that they are integral to so many of the ecological processes we depend upon (like pollination and decomposition), but that wasn’t always the case. Now I have a better understanding of how many other animals use insects as a food source (including humans) and how insects alter the environments around them, but, when I was growing up, in large part I simply classified them as “creepy” (and I will admit there are still a few groups that, although more respected now, are still seen that way). Even as a child, though, there were still certain insects that I found amazing- caterpillars (plus the moths and butterflies they became) were fun to watch, I liked catching ladybugs so they could crawl on my hands and arms, and fireflies were one of the greatest elements of an August summer night where I grew up in New Hampshire. I was mesmerized by the sheer number of glowing insects spread across the fields around the house where we lived- it was magical (and we would try to collect fireflies on our clothing so that we could glow as well).
I have heard that fireflies are not as common as they used to be, and certainly, as an adult, I have never seen the same scenes that were such a regular feature of my childhood. My guess is that pesticides and changes in land use are in some way involved, but I’ve also heard that light pollution is an issue with regard to fireflies. What I know about fireflies is pretty basic: males and females signal as part of the search for a reproductive partner, we usually saw the greatest number of insects in mid-summer, and we saw them in meadows rather than woods; that’s not much to work with, and I don’t even know what they eat when they aren’t busy signaling to each other.
So this month I will be looking into the status of fireflies around the world, trying to get a sense of why we should pay attention to firefly conservation and what the biggest threats are to their survival. Hopefully I can shed a little light on some creatures that were never on my “creepy” list but were also never thought of as a conservation concern.
