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Ponds Against Climate Change

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From Antarctica to the tropics, ponds are widespread habitats found in nearly all terrestrial biomes (Jeffries, 2016). Research estimates that there are 304 million natural lakes and ponds worldwide, covering a total area of approximately 4.2 million km2 (Downing et al., 2006). This article will focus on ponds: according to limnologists, the difference between ponds and lakes is that ponds are shallow enough that plants could grow across the entire surface meaning that it has a photic zone where sun can reach the bottom. By contrast, lakes have an aphotic zone meaning there are sections deep enough that sunlight cannot reach the bottom. Ponds are biodiversity hotspots for both aquatic and terrestrial species, providing habitat for rare specialists such as fairy and tadpole shrimp. Not only are they vital for these species, but they are also vital in managing landscapes from threats such as flooding and climate change. It is known that aquatic ecosystems have a large role in managing greenhouse gases, with oceans among the most well-known of carbon sinks. However, with lakes and ponds covering such a vast expanse of area, is it possible that they are the climate’s unsung heroes?

Carbon sinks are reservoirs that absorb and store atmospheric carbon through physical and biological processes. One study concludes that ponds may be more active in nearly all of these processes than large lakes, marine ecosystems and terrestrial ecosystems (Downing, 2010). Carbon burial rates between ponds can vary depending on composition. Ponds are not ubiquitous, thus the effectiveness of carbon sequestration varies per site depending on factors such as substrate type and vegetation. Gilbert et al., (2014) found that permanent and naturally vegetated ponds were the most efficient at sequestering carbon dioxide, particularly those dominated by thick moss swards and aquatic grasses. These form a thick, moist blanket when the pond dries out, minimising the release of stored carbon into the atmosphere. The least efficient ponds were temporary, shallow arable ponds which lacked vegetation and were regularly disturbed. When discussing the value of ponds in carbon sequestration, it may be unhelpful to group all ponds together as their importance can vary considerably based on their composition. Furthermore, it is important to note that ponds can serve a variety of purposes. Whilst ponds capturing excess fertilisers and pesticides are useful in the fight against climate change, they may not make good wildlife ponds or facilitate biodiversity.

This diversity of ponds is reflected in the range of carbon sequestration rates found across the literature. One study found that small ponds sequester 79-247g of organic carbon per square meter annually, a rate 20-30 times higher than woodlands, grasslands and other habitat types (Taylor et al., 2019). Céréghino et al., (2014) suggested that some 500m2 ponds may even be capable of sequestering up to 1000kg of carbon per year, as much as a car would produce in that time. Although ponds only take up 0.0006% of land area in the UK, a tiny proportion compared to the 36% of grasslands (Carey et al., 2008), their high rates of carbon burial suggest that their overall contribution is significant – even when compared to much larger habitats. Thus their role in tackling climate change should not be overlooked.

Biological processes carried out by aquatic vegetation are pivotal in carbon sequestration in ponds. Photosynthesis contributes to the sequestration of carbon dioxide by turning it into oxygen and biomass. One kilogram of algae uses an average of 1.87 kilograms of carbon dioxide a day (Anguselvi et al., 2019). Algae in ponds also contribute to reducing additional greenhouse gases such as nitrous oxide (N2O). Nitrogen is a key component in chlorophyll and thus used in farm fertiliser. Excess nitrogen could react with oxygen in the air to become N2O. The presence of algae in farm ponds to capture this excess can prevent this reaction from occuring and limit emission of the greenhouse gas. A study has found that two thirds of farm ponds act as N2O sinks (Webb et al., 2019), making them an important contributor to combating climate change, particularly as N2O traps heat at 300x the rate of CO2. 

Ponds play an important role in mitigating climate change, however, there is evidence to suggest that they can also act as carbon sources. Does this offset their sequestering benefits? Take for instance, permafrost thaw ponds. Permafrost thaw ponds in northern regions can be particularly prominent sources of carbon. As permafrosts thaw, vast amounts of carbon dioxide and methane are released, resulting in the formation of small ponds which become carbon emission hotspots (Kuhn, 2018). Although they are releasing carbon, it is not the pond itself creating these gases. Global warming is causing the permafrosts to thaw out and release the stored carbon. Although the ponds facilitate the emissions, it is perhaps misleading to label them as a carbon source in these instances. 

Large habitats such as oceans and woodlands are well-known for their role in reducing greenhouse gasses and mitigating the effects of climate change, but ponds may play an equally important and largely underappreciated role. Ponds are also a fantastic tool against climate change because they give people a way in which to take action. People can easily create ponds in their own gardens and community spaces, and in this way play a part in reducing greenhouse gas emissions and contribute to the global fight against climate change.

Written by Mirran Trimble & Emily Robinson

 

References

Anguselvi, V., Masto, RE., Mukherjee, A., & Singh, PK. (2019) CO2  Capture for industries by algae, Algae, Yee Keung Wong, IntechOpen, DOI: 10.5772/intechopen.81800. Available from: https://www.intechopen.com/books/algae/co-sub-2-sub-capture-for-industries-by-algae

Carey, PD., Wallis, S., Chamberlain, PM., et al. (2008) Countryside Survey: UK results from 2007. Swindon, UK: Natural Environment Research Council.

Céréghino, R., Boix, D., Cauchie, HM., et al. (2014) The ecological role of ponds in a changing world. Hydrobiologia. 723, 1–6.

Downing, JA. (2010) Emerging global role of small lakes and ponds: little things mean a lot. Limnetica. 29(1), 9-24.

Downing, JA., Prairie, YT., Cole, et al. (2006) The global abundance and size distribution of lakes, ponds, and impoundments. American Society of Limnology and Oceanography. 51(5), 2388-2397.

Gilbert, PJ., Taylor, S., Cooke, DA., et al. (2014) Variations in sediment organic carbon among different types of small natural ponds along Druridge Bay, Northumberland, UK. Inland Waters. 4(1), 57-64.

Jeffries, MJ. (2016) Flood, drought and the inter-annual variation to the number and size of ponds and small wetlands in an English lowland landscape over three years of weather extremes. Hydrobiologia. 768, 255–272.

Kuhn, M., Lundin, EJ., Giesler, R., et al. (2018) Emissions from thaw ponds largely offset the carbon sink of northern permafrost wetlands. Scientific Reports. 8, 9535.

Taylor, S., Gilbert, PJ., Cooke, DA., et al. (2019) High carbon burial rates by small ponds in the landscape. Frontiers in Ecology and the Environment. 17(1), 25-31.

Webb, JR., Hayes, NM., Simpson, GL. et al. (2019) Widespread nitrous oxide undersaturation in farm waterbodies creates an unexpected greenhouse gas sink. PNAS. 116(20), 9814-9819.

 

The effect of the climate crisis on UK reptile populations

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Back in 2018 we discussed some of the impacts of climate change on amphibians worldwide (Froglife 2018). Since then, climate change has continued to accelerate, with global average temperatures in 2020 more than 1oC warmer relative to pre-industrial levels. The 2015 Paris Agreement has not, so far, caused nations to reduce their emissions anywhere near fast enough (Global Carbon Project 2020). The extent of future warming is projected to reach somewhere between 2 – 4oC or above, dependent upon a range of scenarios (IPCC 2014). The magnitude and speed of this change is unprecedented, and the impacts upon wildlife are already being seen.

We know that wildlife and their habitats – collectively termed the ‘biosphere’ – are in a fine, dynamic and interconnected balance. Unpicking the exact drivers of population changes is not straightforward, because they themselves are interacting in complex ways. What’s clear is that climate change is an additional stress factor for wildlife worldwide, on top of (and often accelerating) habitat loss and fragmentation, pollution and the impact of invasive species. In the UK climate change is predicted to cause hotter, drier summers and warmer, wetter winters. There will be greater extremes of weather, as well as sea level rise (Met Office 2019).

So how might the UK’s terrestrial reptiles be affected by climate change?
To begin to answer this, we can consider the direct effects of climate change on reptile physiology and behaviour, and indirect impacts from changing trophic interactions (populations of predators and prey), and from changes to reptile habitats (Le Galliard et al. 2012).

UK reptiles are more or less at the northernmost edge of the range for their species, although the adder, common lizard and slow worm have Scandinavian populations at higher latitudes. These three species are viviparous, meaning embryos develop within the body of the adult and born live. The smooth snake is ovoviviparous, which can be described as a more primitive form of viviparity, where the eggs develop within the mothers body. Sand lizards and grass snake are oviparous, meaning they lay their eggs externally, and embryos are therefore more reliant on environmental factors for their development. 

All UK reptiles however, have cousins residing in the warmer southerly climes of Iberia and Central Europe and the Balkans. So, we could assume that warmer climate here will improve survival in existing reptile populations, while enabling a northward shift of their distributions. Unfortunately, the reality is not that simple. Dunford and Berry (2012) modelled UK reptile population changes under low and high emissions scenarios for 2050 and 2080. Grass snakes appeared to be the only species consistently predicted to shift northward while maintaining the majority of their present distribution (see Cathrine, 2014 for tantalising evidence of Scottish grass snake populations), while slow worms showed a mixed northward shift with a contraction of southern populations. For all other species modelling predicted widespread population decline, greater under a higher emissions scenario (Dunford and Berry 2012).

Being ectothermic, reptiles are highly sensitive to their environment, with a tight bell curve describing their optimal climatic conditions (Le Galliard et al. 2012). Temperature and rainfall strongly influence reptile behaviour, and a changing climate has great potential to create mismatches – for example if temperature and rainfall is suboptimal either for reptiles or their prey species, especially at key points in the year such as hibernation emergence. Climate change is already affecting reptile prey populations and will continue to do so. For example Ewald et al. (2015) identified numerous invertebrate groups demonstrating sensitivity to extreme climate events over the last four decades. These trends must be considered alongside the ongoing impact of other pressures, particularly pesticide use (van Klink et al. 2020), all of which creates a complex picture. Climate impacts will vary between species groups and depend upon other biogeographical factors, meaning that impacts will not be the same everywhere for a given species.

In the UK, warming should increase reptile growth and maturation rates, due to longer periods of activity. Milder winters will likely reduce hibernation lengths for our reptiles. Earlier spring emergence, and activity extending further into the autumn and winter months would likely bring reproduction forward in the year, as gestation and incubation length is generally shorter in warmer climates. Larger body sizes in warmer climates may result in greater reproductive success (Le Galliard et al. 2012). Warm temperatures also enable a greater number of number of broods per year, observed in slow worms (Smith 1990), and common lizards (Bestion et al. 2015). However, life cycle changes may have additional impacts on population demographics and survival. Bestion et al. (2015) created experimental common lizard populations in climate-controlled chambers, with populations either subject to current average temperatures or those matching IPCC predictions for the coming century. Warming increased growth rates, brought reproduction forward, and resulted in a higher number of broods per season. However, this life cycle acceleration was coupled with a reduction in adult survival rates. Of several possible causes, the authors proposed the most likely to be greater metabolic requirements for larger individuals, with warmer temperatures increasing energetic requirements which could not be met fully by increased foraging, particularly when warm weather restricted their activity.

Our fragmented UK landscape creates major barriers for all wildlife. Reptile species are generally philopatric (tending to return to or remain near the same particular area), and so are especially sensitive to habitat loss, with populations often centred around relatively small habitat pockets or managed reserves. So even if a warmer climate could result in populations expanding northward, whether this will occur in reality depends on whether there are routes and habitats for them to do so. Araujo et al. (2006) simulated climate change driven UK reptile population dynamics under assumptions of unlimited and zero dispersal ability. Unlimited dispersal resulted in population expansion, with some local extinctions in southerly locations. Zero dispersal resulted in population contractions for all UK species, indicating climate change driven population collapse. This demonstrates the importance of considering all factors influencing population viability and dispersal in combination with climate change pressures.

Adders are usually reliant on specific habitat patches and are highly sensitive to habitat destruction and hibernation area disturbance due to their low recolonization abilities, even relative to other reptile species. On a local level, given typically small population sizes and low mobility, climate change driven habitat quality declines could result in local extinctions particularly as they may not have suitable adjacent habitat, nor the inclination to move (Gleed-Owen and Langham 2012). Although McInerny (2018) indicates that implementing appropriate mitigation can enable adder populations to persist alongside human modifications to local habitats, the adders ongoing decline nationwide is concerning (Baker et al. 2002, Gardner et al. 2019), which even a low emissions climate change scenario is likely to exacerbate (Dunford and Berry 2012).

adder


The dual pressures of habitat loss and climate change are even more apparent for our two most limited reptiles, the sand lizard and the smooth snake. Sand lizards can be found on lowland heath as well as coastal sand dunes. Smooth snakes are only known to be present on lowland heath in the south of England. Populations are generally isolated with little capacity for dispersal, creating a barrier to adaptation to changing conditions. Climate change could threaten habitat quality, for example increased frequency of heavy rainfall events could destroy sand lizard nests and reduce juvenile survival rates (Edgar and Bird 2006), while increased fire prevalence and sea level rise could destroy important habitat features. Dunford and Berry (2012) paint a particularly dire picture for the sand lizard, as its reliance upon highly specific landscape features such as south facing slopes and complex habitat mosaics makes the species highly sensitive to habitat loss. A small population of sand lizards has persisted on the Scottish Isle of Coll, since their introduction for research in the 1970s. Comparing the climate change resilience of this northern and relatively isolated population with that of other UK populations will be an interesting topic for study over the next few decades.

Heathland habitats are one of our most heavily impacted by urbanisation in the UK. Although direct loss through land-use change is now controlled by planning and environmental legislation, development in surrounding areas continues to increase pressure on remaining isolated heathland patches, through increased fire risk, predation by domestic animals and disturbance (Hayhow et al. 2019). Fagundez (2013) describes further pressures facing heathlands under climate change, including fires, and shifts in vegetation composition. We are used to a static conservation model for our heaths. As climate change progresses, the ideal climatic conditions for heath will likely expand in Britain (Thomas et al. 1999), and Loidi et al. (2010) point out that extensive lowland heaths throughout southern Europe support a greater diversity of reptiles than we see here. However, whether habitats will be able to expand is an entirely human choice (Coll et al. 2016, Hayhow et al. 2019).

All of the pressures we have presented here are anthropogenic in origin, born from human choices, and our expectations of how we can and should manage the land and its resources. The enormity of shifting these practices cannot be underestimated, but at least it is within our abilities to do it!

Written by Zak Mather-Gratton 

References
Araújo, M.B., Thuiller, W. and Pearson, R.G., 2006. Climate warming and the decline of amphibians and reptiles in Europe. Journal of biogeography, 33(10), pp.1712-1728.

Baker, J., Suckling, J. and Carey, R., 2002. Status of the adder Vipera berus and the slow-worm Anguis fragilis in England. English Nature.

Bestion, E., Teyssier, A., Richard, M., Clobert, J. and Cote, J., 2015. Live fast, die young: experimental evidence of population extinction risk due to climate change. PLoS Biol, 13(10), p.e1002281.

Cathrine, C., 2014. Grass Snakes (Natrix natrix) in Scotland. Glasgow Naturalist, 26(Part 1), pp.36-40.

Coll, J., Bourke, D., Hodd, R.L., Skeffington, M.S., Gormally, M. and Sweeney, J., 2016. Projected climate change impacts on upland heaths in Ireland. Climate Research, 69(2), pp.177-191.

Dunford, R.W. and Berry, P.M., 2012. Climate change modelling of English amphibians and reptiles: Report to Amphibian and Reptile Conservation Trust (ARC-Trust).

Edgar, P. and Bird, D.R., 2006. Action plan for the conservation of the Sand Lizard (Lacerta agilis) in Northwest Europe. Document T-PVS/Inf (2006), 18.

Ewald, J.A., Wheatley, C.J., Aebischer, N.J., Moreby, S.J., Duffield, S.J., Crick, H.Q. and Morecroft, M.B., 2015. Influences of extreme weather, climate and pesticide use on invertebrates in cereal fields over 42 years. Global Change Biology, 21(11), pp.3931-3950.

Fagúndez, J., 2013. Heathlands confronting global change: drivers of biodiversity loss from past to future scenarios. Annals of Botany, 111(2), pp.151-172.

Froglife 2018. Amphibians and Climate Change. Croaking Science
Gardner, E., Julian, A., Monk, C. and Baker, J., 2019. Make the adder count: population trends from a citizen science survey of UK adders. Herpetological Journal, 29, pp.57-70.

Gleed-Owen, C. and Langham, S., 2012. The Adder Status Project–a conservation condition assessment of the adder (Vipera berus) in England, with recommendations for future monitoring and conservation policy.

Report to Amphibian and Reptile Conservation. ARC, Bournemouth, UK.
Global Carbon Project. 2020. Carbon budget and trends 2020. [www.globalcarbonproject.org/carbonbudget] published on 11 December 2020

Hayhow, D.B., Eaton, M.A., Stanbury, A.J., Burns, F., Kirby, W.B., Bailey, N., Beckmann, B., Bedford, J., Boersch-Supan, P.H., Coomber, F. and Dennis, E.B., 2019. State of nature 2019.

IPCC, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp.

van Klink, R., Bowler, D.E., Gongalsky, K.B., Swengel, A.B., Gentile, A. and Chase, J.M., 2020. Meta-analysis reveals declines in terrestrial but increases in freshwater insect abundances. Science, 368(6489), pp.417-420.

Le Galliard, J.F., Massot, M., Baron, J.P. and Clobert, J., 2012. Ecological effects of climate change on European reptiles. Wildlife conservation in a changing climate, pp.179-203.

Loidi, J., Biurrun, I., Campos, J.A., García‐Mijangos, I. and Herrera, M., 2010. A biogeographical analysis of the European Atlantic lowland heathlands. Journal of Vegetation Science, 21(5), pp.832-842.

McInerny, C.J., 2019. The study and conservation of adders in Scotland. The Glasgow Naturalist Volume 27, p.67.

Met Office, 2019. UK climate projections: Headline findings.
Smith, N.D., 1990. The ecology of the slow-worm (Anguis fragilis L.) in southern England. Doctoral dissertation, University of Southampton.

Thomas, J.A., Rose, R.J., Clarke, R.T., Thomas, C.D. and Webb, N.R., 1999. Intraspecific variation in habitat availability among ectothermic animals near their climatic limits and their centres of range. Functional Ecology, 13, pp.55-64.

Croaking Science: Amphibians and Climate Change

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Amphibians and climate change

Over the past few decades rising global temperatures and associated climate change have been of increasing concern due to rises in atmospheric carbon dioxide and other greenhouse-gas emissions. Over the past century global temperatures have risen on average by 0.7°C and these have been greatest in the last few decades (IPCC, 2007). This has resulted in a range of global climatic changes which have had varied impacts on amphibian species. For example, several species of amphibian have become extinct in southeast Brazil due to the occurrence of frost, and the decline in several tropical amphibian species has been attributed to unusually dry conditions (Blaustein et al. 2010). In the UK an increase in the prevalence of mild and wet winters has negatively affected the common toad Bufo bufo (Reading, 2007) (Figure 1). Range shifts, where species are either forced to higher latitudes or altitudes are a particular problem for many species within Central and South America where there are a high number of range-restricted species. Here, temperatures are predicted to become hotter and drier and may result in species extinctions if there is no other suitable habitat available to expand into. Other potential direct impacts of climate change on amphibians are decreased survival such as that reported in the common toad (Reading, 2007), changes in developmental rates of eggs and larvae, and changes in behaviour of adults and larvae (Blaustein et al. 2010).

Figure 1 The common toad Bufo bufo is susceptible to changing winter temperatures in the UK. (Photo ©Froglife)

Changes in the timing, or phenology, of amphibian breeding have been intensively studied in a range of species across the globe. Within the UK, many studies have shown a trend for earlier breeding in the common frog Rana temporaria, common toad Bufo bufo, natterjack toad Epidalea calamita and two species of newts (smooth newt Lissotriton vulgaris and great crested newt Triturus cristatus). However, findings from several independent studies reveal that the impacts of a changing climate on breeding times may be more complex. For example, Beebee (2002) reported results of thirty years of studying populations of the common frog and found no trend for earlier breeding. Beebee (2002) reported that the two explosive breeding amphibians in the UK, common frog and common toad, showed relatively minimal changes in breeding date. However, the protracted breeders, natterjack toad and newt species showed significantly earlier breeding times (Figure 2). Beebee (2002) predicted that this could have important community effects. Earlier arrival of newts at ponds may increase predation on common frog spawn and this in turn may result in local population declines of the common frog. Similar findings have been found by Reading (1998) who found no evidence of earlier breeding in a population of the common toad. More recent studies have concluded contrasting results. For example, Scott et al. (2008) studied the phenology of the common frog and did find a trend for earlier breeding. However, the authors noted no trend for earlier hatching dates. In addition, Carroll et al. (2009) reported findings from a study from the UK Phenology Network which collected nearly 70,000 records of the first spawn dates of the common frog across the UK between 1998 and 2007. On average, the pattern of spawning followed a consistent pattern across the UK with first spawning dates earliest in the south west and progressively later in the north and east. Although there was variation in spawning dates between years, on average there was a trend for the common frog to breed 10 days earlier at the end of the period. In a more recent study carried out by Loman (2016) in Sweden, local variation in pond conditions was of key importance in determining spawning date of the common frog and in particular pond water temperature, as oppose to air temperature. In addition, Loman (2016) found that the number of frogs breeding at a pond had a significant impact on breeding date. Common frogs spawned earlier in ponds with a higher, rather than lower, number of breeding pairs. For example, a pond with only five breeding individuals spawned 7.2 days later than ponds with 500 individuals (Loman, 2016). Therefore population sizes, as well as climatic changes, may need to be considered when investigating the potential impacts on amphibian breeding phenology.

Figure 2 Great crested newts Triturus cristatus are responding to milder winters by arriving at ponds earlier in the year. (Photo © Froglife)

In addition to the above direct effects of climate change, there are a number of potential indirect effects, such as variations in larval food availability. The larvae of many species of anurans depend on plentiful supplies of algae but rising temperatures in water bodies may trigger early blooms of detrimental filamentous cyanobacteria which may prove detrimental to feeding and growth. In addition, many salamanders and newts rely on small aquatic invertebrates and research by Durance & Ormerod (2007) has found that in the UK, spring macroinvertebrate abundance in headwater streams might decline by 21% for every 1 °C rise in water temperature, which highlights the sensitivity of headwater stream ecosystems to climate change. Finally, emerging infectious diseases have had wide-ranging and negative impacts on amphibian populations across the globe. In particular, chytrid fungus caused by Batrachochytrium dendrobatidis (BD) has been implicated as the proximate cause for crashes in many members of the tropical genus of Atelopus frogs. Pounds et al. (2006) have suggested that changing climatic conditions in mountainous areas of Central and South America have resulted in night time temperatures that have shifted closer to the optimal temperature for BD, while increased daytime cloudiness prevents frogs from finding thermal refuges from the pathogen. This has increased the prevalence of the disease and precipitated declines in many Atelopus species.

The impacts of climate change on amphibian populations are complex with many potential direct and indirect impacts on amphibians at individual and population scales. Global temperatures are predicted to increase by between 1.1 and 6.4 °C by 2100 (IPCC, 2007), so coherent research and conservation measures are required to preserve populations of amphibians across the globe.

References

Beebee, T.J.C. (2002) Amphibian phenology and climate change. Conservation Biology, 16 (6): 1454-1455.

Blaustein, A.R., Walls, S.C., Bancroft, B.A., Lawler, J.J., Searle, C.L. & Gervasi, S.S. (2010) Direct and indirect effects of climate change on amphibian populations. Diversity, 2: 281-313.

Carroll, E.A., Sparks, T.H., Collinson, N. & Beebee, T.J.C. (2009) Influence of temperature on the spatial distribution of first spawning dates of the common frog (Rana temporaria) in the UK. Global Change Biology, 15 (2): 467-473.

Durance, I. & Ormerod, S.J. (2007) Climate change effects on upland stream macroinvertebrates over a 25-year period. Global Change Biology, 13: 942-957.

IPCC. (2007) Climate change 2007: the physical science basis. In Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Eds: S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Avery, M. Tignor & H.L Miller. Cambridge University Press, Cambridge, UK.

Loman, J. (2016) Breeding phenology in Rana temporaria. Local variation is due to pond temperature and population size. Ecology and Evolution, 6 (17): 6202-6209.

Pounds, A., Bustamante, M.R., Coloma, L.A., Consuegra, J.A., Fogden, M.P.L., Foster, P.M., La Marca, E., Masters, K.L., Merino-Viteri, A., Puschendorf, R., Ron, S.R., Sánchez-Azofeifa, G.A., Still, C.J., Young, B.E. (2006) Widespread amphibian extinctions from epidemic disease driven by global warming. Nature, 439: 161-167.

Reading, C.J. (1998) The effect of winter temperatures on the timing of breeding activity in the common toad Bufo bufo. Oecologia, 117 (4): 469-475.

Reading, C.J. (2007) Linking global warming to amphibian declines through its effects on female body condition and survivorship. Oecologia, 151: 125-131.

Scott, A.W., Pithart, D. & Adamson, J.K. (2008) Long-term United Kingdom trends in the breeding phenology of the common frog, Rana temporaria. Journal of Herpetology, 42 (1): 89-96.

Croaking Science: The Golden Toad

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 As our Common Toads start to enter hibernation after a tricky weather year; Becky Austin our Croaking Science Volunteer, talks about how climate change affected one of their cousins in Costa Rica.

The very first species whose extinction was blamed on climate change due to anthropogenic causes was an amphibian: the Golden Toad. Once abundant in a small area of the Costa Rican cloud forests of Central America, the last individual sighting was in 1989 and in 2004, the toad was stated as extinct.

Golden Toads, or Bufo periglenes, were only 5cm long and showed sexual dimorphism: males had bright ‘golden’ skin, whereas females had olive skin with red spots and a yellow rim. Golden toads also showed the extraordinary feature of ‘gastric breeding’, where eggs were kept in the stomach of the female until the tadpoles were ready to leave via the mouth.

How was climate change to blame for the extinction of this fascinating species? Recent discoveries may show that the toad’s extinction coincided with a very dry period of time caused by an El Niño event in 1986-7 (where a warm Pacific current affected the South American climate). This caused breeding pools to dry out and population numbers to crash as few tadpoles could survive. However, this alone may not be the cause.

Gobal warming is causing consistent atmospheric temperature changes in most parts of the world, including the toad’s home range in Costa Rica. Many scientists believe that in these highland areas, conditions are increasingly becoming more suited to the prolific growth of the chytrid fungus Batrachochytrium dendrobatidis, which may have caused the extinction of the golden toad. Even if the fungus initially spread due to the conditions the El Niño caused in the late 80s, continual warming will increase the fungus’s rate of destruction, leading to many further amphibian extinctions. Global warming must therefore be addressed as quickly as possible as the root of many species extinctions.

 

By Charles H. Smith, vergrößert von Aglarech (U.S. Fish and Wildlife Service) [Public domain]
By Charles H. Smith, vergrößert von Aglarech (U.S. Fish and Wildlife Service) [Public domain]
 

What can you do to help?

Check out our website and get clued up about chytrid fungus and what it looks like; so you can report any potential sightings of the disease.

Donate to Froglife this year and help us continue our work with amphibians and reptiles in 2014

References

Pounds, J.A., Bustamante, M.R., Coloma, L.A., Consuegra, J.A., Fogden, M.P.L., Foster, P.N., La Marca, E., Masters, K.L., Merino-Viteri, A., Puschendorf, R., Ron, S.R., Sanchez-Azofeifa, G.A., Still, C.J. and Young, B.E. (2006). Widespread amphibian extinctions from epidemic disease driven by global warming. Nature, 439: 161-167.

Anchukaitis, K.J . and Evans, M.N. (2010). Tropical cloud forest climate variability and the demise of the Monteverde golden toad. PNAS, 107: 5036-5040.

 

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