Category Archives: Climate Change/Global Warming
Standing Still in Running Water: Lotic Dragon and Damselfly Species Less Able to Adapt to Climate Change
The Hairy Hawker (Brachytron pratense) is adapted to standing water habitats. It belongs to the family of Aeshnidae. (Credit: Image courtesy of Senckenberg Research Institute and Natural History Museum)
ScienceDaily (Mar. 5, 2012) — A study published online in Biology Letters throws light on the capability of individual dragonfly species to track climate change. The authors show that dragonfly species which breed in pools and ponds are better able to cope with climate change than species whose habitats are streams and rivers. The results are based on a comparison of the projected and observed distributions of European dragonfly species in 2006 and 1988.
The study was conducted at the German Biodiversity and Climate Research Center and the Danish Centre for Macroecology, Evolution and Climate, and in cooperation with various other European research institutes.
Many dragonfly species have preferred freshwater habitats. Whereas larvae of some species are only to be found in standing (lentic) freshwater habitats such as pools, ponds and lakes, there are also species particularly adapted to running (lotic) freshwater habitats. Does the choice of habitat have consequences for the evolution of dispersal abilities and thus the potential to track climate change?” To find out we compiled data of 88 European dragonfly species and analyzed whether the observed distribution is consistent with what our models tell us about the potential distribution in Europe” says lead author Dr. Christian Hof, BiK-F, about the study design.
Habitat-stability influences dispersal abilities
Comparing the two sets of species the scientists found that lentic dragon- and damselfly species fill their potential range, i.e. the climatically suitable areas, to a higher extent than lotic species. According to the researchers, the species’ different dispersal abilities are due to the lower habitat persistence of standing waters. In the long term it is more likely for pools and pond to disappear as a habitat than a stream or a river. To make up for this risk, lentic dragonfly species have evolved a higher dispersal ability.
Lentic species better able to track climate change
If lentic species are stronger dispersers than lotic species they should also be able to track climate changes more rapidly because the higher the mobility the higher the chance of a change in range. This hypothesis was proven right by comparing observed and projected distributions for 2006. Models based on datasets from 1988 over-predicted lotic species ranges in 2006 indicating that the lower dispersal abilities of lotic species hinder them from filling their climatically suitable range. The tendency for over-prediction was less pronounced for lentic species.
Generalizations for the entire species have to be revised
With a maximum velocity of up to 40 km per hour and travel distances of up to 1,000 km within a few days, dragon- and damselfly species are strong fliers and highly mobile. This has led to the assumption that they will probably survive even drastic climatic changes. “Our results regarding the different dispersal abilities of these species in relation to their habitat preference imply that generalizations for entire species groups about their ability to respond to climate change may be misleading.” says Hof who conducted the study in collaboration with colleagues from the Philipps-Universität Marburg, Germany, the Center for Macroecology, Evolution and Climate, Copenhagen, Denmark and the National Museum for Natural Sciences in Madrid, Spain.
- C. Hof, M. Brandle, D. M. Dehling, M. Munguia, R. Brandl, M. B. Araujo, C. Rahbek. Habitat stability affects dispersal and the ability to track climate change. Biology Letters, 2012; DOI: 10.1098/rsbl.2012.0023
ScienceDaily (Jan. 12, 2012) — Wandering albatrosses have altered their foraging due to changes in wind fields in the southern hemisphere during the last decades. Since winds have increased in intensity and moved to the south, the flight speed of albatrosses increased and they spend less time foraging. As a consequence, breeding success has improved and birds have gained 1 kilogram. These are the results of the study of an international research team published in the latest issue of the Science journal. However, these positive consequences of climate change may last short if future wind fields follow predictions of climate change scenarios, researchers warn.
For this study, biologists had combined data on the duration of foraging trips and breeding success over the last 40 years, as well as foraging and body mass over the last 20 years of wandering albatross (Diomedea exulans) breeding in Crozet Islands. This archipelago lies approximately in the heart of the southern Indian Ocean (halfway between Madagascar and Antarctica). It belongs to the French Southern Territories and it is located in the windiest part of the Southern Ocean. The new findings are the result of an international research team from the French National Centre for Scientific Research (CNRS-CEBC) and the German Helmholtz-Centre for Environmental Research (UFZ).
Thanks to miniaturised tracking devices, researchers were able to track the foraging movement of albatrosses at a distance of 3500 kilometers from the colony. They found that albatross have altered their search patterns following changes in wind conditions over the past two decades. Females used increasingly more poleward and windy areas for foraging. As a consequence their travel speed increased while the total distance covered during foraging flights did not change. “This means that they spend less time at sea while incubating the egg and thus the breeding success increases” explains Dr. Henri Weimerskirch of the French National Centre for Scientific Research (CNRS-CEBC). Researchers were surprised that both females and males have increased their body mass in one kilogram, which corresponds approximately to one tenth of their total body weight. This could be not only a result of shorter incubation periods on the nest, but also an adaptation to windier conditions.
“The wandering albatross Crozet population has decreased as a result of adult mortality on longline fishing in subtropical waters, especially females since they favour warmer subtropical waters in the north compared to the more southerly distribution of males” says Dr. Maite Louzao Arsuaga, who has been modelling albatross movement from 2009 to 2011 at the UFZ. “Due to the changing wind conditions, females are now foraging in more southward areas where such fishing is not that widespread.” However, the positive effects of changing environmental conditions of the last decades will not last in the future. Climate scenarios predict that westerly winds will move even further south by 2080 and wandering albatrosses might have to fly further to find optimal conditions for flying.
The total population of the wandering albatross is currently estimated at around 8,000 breeding pairs. All populations have shown a decrease at some stage over the last 25 years. This endangered species is threatened primarily by incidental catch in fisheries, especially longline fishing at sea, whereas the introduction of alien species (such as rats or cats) are a key conservation threat for the species on breeding colonies. Additionally, the accumulation of anthropogenic debris such as plastic and fishing hooks on albatrosses have negative effects on their populations. Thus, it is important to continue with monitoring programs of population trends and distribution at sea, as well as to undertake effective conservation measures. The foraging habitat of wandering albatrosses is managed by more than one Regional Fisheries Management Organisations, which makes it difficult to implement conservation measures for the species.
The wandering albatross has fascinated people for centuries. With a wingspan of over three meters and a half, it is the largest seabird in the world, surpassing just the Andean condor (Vultur fulvus). This elegant sailor, which spends most of its life flying, breeds on remote subantarctic islands over the Southern Ocean. They travel thousand of kilometers searching for fish and cephalopods like squids, often following ships and feeding on offal. The plumage of wandering albatrosses is variable, whitening with age. The maximum known age is 55 years old. Since the rearing of chicks takes a whole year, they breed only every second year
Apart from the study published in the latest Science issue, the research team has identified the key marine areas for the conservation of wandering albatrosses in the southern Indian Ocean published in 2011 in the Journal of Applied Ecology. This study provided the first map to support the future development of a network of priority protected areas in the southern part of the Indian Ocean, which are based on habitat predictions. “Because the species has no natural enemies and is at the top of the food web, it is particularly well suited as an indicator of the health of marine ecosystems,” says Dr. Thorsten Wiegand from the UFZ, who supervised the work of Dr. Maite Louzao. “This could help not only a single species, but the underlying biodiversity associated with pelagic key habitats to protect Southern Ocean. Moreover, we have developed methods of habitat modelling broadly applicable and can be used to assess changes in species distribution within the current global change scenario.”
- H. Weimerskirch, M. Louzao, S. de Grissac, K. Delord.Changes in Wind Pattern Alter Albatross Distribution and Life-History Traits. Science, 2012; 335 (6065): 211 DOI: 10.1126/science.1210270
- Maite Louzao, David Pinaud, Clara Péron, Karine Delord, Thorsten Wiegand, Henri Weimerskirch. Conserving pelagic habitats: seascape modelling of an oceanic top predator. Journal of Applied Ecology, 2011; 48 (1): 121 DOI: 10.1111/j.1365-2664.2010.01910.x