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Tag: Ecosystems

Living on the Edge: Habitat Fragmentation in Our Rainforest Ecosystems

Posted on by Leah Line

The Brazilian Atlantic rainforest is made up of some of the most important ecosystems on earth (Magnago et al., 2014). It supports species that are not found anywhere else on the planet (Ribeiro et al., 2009). However, the rainforest is not the vast expanse of green canopy that you might imagine.

In fact, deforestation has divided the landscape. Now, more than 80% of the remaining forest is made up of fragments with an area of less than 50 hectares (Ribeiro et al., 2009). Almost half is less than 100 metres from its edges (Ribeiro et al., 2009).

Deforestation leads to isolated fragments of rainforests. Source: Bierregaard, 2016
Deforestation leads to isolated fragments of rainforests. Source: Bierregaard, 2016

The situation in the Brazilian Atlantic rainforest is not uncommon. Due to fragmentation, more than 70% of the world’s forests are now within 1 kilometre of a forest edge, impacting rainforest ecosystems across the globe (Haddad, 2015).

WHAT IS HABITAT FRAGMENTATION?

Habitat fragmentation is the division of a habitat into increasingly smaller and more isolated pieces (Haddad, 2015). In rainforest ecosystems, this is done through deforestation. Fragmentation effects the entire ecosystem, by reducing forest area, increasing isolation and increasing forest edges (Haddad, 2015).

EDGE EFFECTS

Edge effects are the ecological changes that occur at the boundaries of these habitat fragments (Laurance et al., 2016). They can include (Laurance et al., 2016)

–  Increased wind damage
–  Changes in temperature and humidity
–  Increased flooding

These effects may make the environment along the edges of fragments unsuitable for certain species, making their available habitat even smaller (Turner, 1996).

As forests become increasingly fragmented, their exposure to edge effects also increases. Source: www.summitlearning.org
As forests become increasingly fragmented, their exposure to edge effects also increases. Source: www.summitlearning.org

THE HABITAT MATRIX

The landscape surrounding forest fragments is referred to as a “matrix” of habitats (Haddad, 2015; Gascon et al., 1999). The matrix plays an important role in acting as a selective filter for the movement of species between fragments (Gascon et al., 1999). Animals that cannot survive the matrix will be unable to move across fragments. This not only makes the animals themselves at risk of decline, but if they play a role in seed dispersal (by transporting plants’ seeds in their faeces, fur or feathers) plants will also be at risk.

“Why did the cassowary cross the road? To disperse seeds.” Cassowaries are important for seed dispersal in the rainforests of New Guinea, but could be threatened due to fragmentation of their habitats. Source: Roberts, 2016
“Why did the cassowary cross the road? To disperse seeds.” Cassowaries are important for seed dispersal in the rainforests of New Guinea, but could be threatened due to fragmentation of their habitats. Source: Roberts, 2016

But, it is not all bad news: studies have found that some species, such as Amazonian frogs, possess traits that allow them to use the matrix for movement and reproduction, as well as allowing them to tolerate edge effects and survive in the remaining fragments (Gascon et al., 1999).

Some species, such as frogs, possess traits that allow them to survive habitat fragmentation in rainforests. Source: Niem, 2015
Some species, such as frogs, possess traits that allow them to survive habitat fragmentation in rainforests. Source: Niem, 2015

LOOKING TO THE FUTURE…

Considering the range of impacts, it is unsurprising that the fragmentation of rainforests is one of the greatest threats to global biodiversity (Magnago et al., 2014). And the future does not look bright; as human populations continue to rise, the extent of deforestation and fragmentation of our forests is likely to also increase (Haddad, 2015).

But all is not lost; conservation projects mitigate some negative impacts, with studies discovering types of forest that can reduce edge effects near fragment margins (Mesquita et al., 1999).

BUT WHAT CAN I DO?

Take a look at the following website by Greenpeace and see what you can do to prevent deforestation: http://www.greenpeace.org/usa/forests/solutions-to-deforestation/

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References

Bierregaard, R., 2011. Forest fragments under research in the Biological Dynamics of Forest Fragments Project. [photograph] Reproduced in: Hance, J., 2011. Lessons from the world’s longest study of rainforest fragments. [online] Available at: https://news.mongabay.com/2011/08/lessons-from-the-worlds-longest-study-of-rainforest-fragments/ [Accessed: 21/03/17]

Gascon, C.; Lovejoy, T. E.; Bierregaard, R. O.; Malcolm, J. R.; Stouffer, P. C.; Vasconcelos, H. L.; Laurance, W. F.; Zimmerman, B.; Tocher, M. and Borges, S., 1999. Matrix habitat and species richness in tropical forest remnants. Biological Conservation, 91(2-3), pp. 223-229

Haddad, N. M.; Brudvig, L. A.; Clobert, J.; Davies, K. F.; Gonzalez, A.; Holt, R. D.; Lovejoy, T. E.; Sexton, J. O.; Austin, M. P.; Collins, C. D.; Cook, W. M.; Damschen, E. I.; Ewers, R. M.; Foster, B. L.; Jenkins, C. N.; King, A. J.; Laurance, W. F.; Levey, D. J.; Margules, C. R.; Melbourne, B. A.; Nicholls, A. O.; Orrock, J. L.; Song, D. and Townshend, J. R., 2015. Habitat fragmentation and its lasting impact on Earth’s ecosystems. Science Advances, 1(2), pp. 1-9

Laurance, W.F.; Camargo, J. L. C.; Fearnside, P. M.; Lovejoy, T. E.; Williamson, G. B.; Mesquita, R.C.G.; Meyer, C. F. J.; Bobrowiec, P. E. D. and Laurance, S.G.W., 2016. An Amazonian forest and its fragments as a laboratory of global change. pp. 407-440. In: L. Nagy, B. Forsberg, P. Artaxo (eds.) Interactions Between Biosphere, Atmosphere and Human Land Use in the Amazon Basin. Springer (Ecological Studies 227), Berlin, Alemanha.

Magnago, L. F. S.; Edwards, D. P.; Edwards, F. A.; Magrach, A.; Martins, S. V. and Laurance, W. F., 2014. Functional attributes change but functional richness is unchanged after fragmentation of Brazilian Atlantic forests. Journal of Ecology, 102(2), pp. 475-85

Mesquito, R. C. G.; Delamônica, P. and Laurance, W. F., 1999. Effect of surrounding vegetation on edge-related tree mortality in Amazonian forest fragments. Biological Conservation, 91(2-3), pp. 129-134

Niem, Y. Tree frog silhouette. [photograph] Available at: http://fotovenopilon.si/entry/jury/awards.php?section=D [Accessed: 22/03/17]

Ribeiro, M. C.; Metzger, J. P.; Martensen, A. C.; Ponzoni, F. J. and Hirota, M. M., 2009. The Brazilian Atlantic Forest: How much is left, and how is the remaining forest distributed? Implications for conservation. Biological Conservation, 142(6), pp. 1141-1153

Roberts, G., 2016. Cassowary on road. [photograph] Available at: http://sunshinecoastbirds.blogspot.co.uk/2016/06/queensland-road-trip-13-etty-bay.html [Accessed: 22/03/17]

Turner, I. M., 1996. Species Loss in Fragments of Tropical Rain Forest: A Review of the Evidence. Journal of Applied Ecology, 33(2), pp. 200-209



Too Close To Home – The Effect Of Urbanisation on Global Wildlife

Posted on by Alexis Alders
Urban fox
Hobson (2015)

 

With increasing urbanisation of once wild landscapes, nature is forced to live right on our doorstep. With reports of vicious seagulls, giant rats, and foxes attacking babies, how is wildlife coping with living in the city?

 

Cities currently comprise around 3% of land globally (Faeth et al., 2011) and as this increases, more research is focusing on the animals we share our cities with. Urban development causes habitat fragmentation, enables the invasion of non-native species, and changes regional climates, which leads to a loss of wildlife. But what effect does the change in the environment have on the remaining flora and fauna?

 

In Mexico City, the number of bird species has decreased, but the number of birds overall has increased (Ortega-Alvarez and MacGregor-Fors, 2009). This was also found in butterflies in Mexico (Ramirez-Restrepo et al. 2015). Another pattern found in cities is a decrease in the number of species in more developed areas (Faeth et al. 2011). Decreases in the number of species towards the city centre is due to the avoidance of increased pollution, noise and light in these areas (Ortega-Alvarez and MacGregor-Fors, 2009). Artificial lighting affects the behaviour of bats (Hale et al 2015) and many species are sensitive to high human disturbance (Ortega-Alvarez and MacGregor-Fors, 2009). Few species can survive in cities, as they are inhospitable environments. Known as generalists, these species can eat food from more than one source and can survive in several habitats. Food is more available in the form of human rubbish (Ortega-Alvarez and MacGregor-Fors, 2009) which supports a larger abundance of animals. However, this increase in numbers is only seen in generalists, which can make use of this resource.

 

Which species can survive in a city is determined by hierarchical theoretical filters based on the environment (Aronson et al., 2016). A diagram of this can be seen below.

Urban hierarchical filters
Fig. 1 (Aronson et al., 2016, pg. 2954)

 

Generalists are more likely to meet these criteria due to flexibility within their characteristics. The structure of cities greatly impacts the species that live within them (Aronson et al. 2016). Management intensity in gardens is the main factor affecting spider communities, while bird communities are significantly affected by the abundance of woody plants (Sattler et al. 2010). Butterfly communities are structured by distance to city centre, and distance to well-preserved habitat both of which are linked to the overall structure of the city (Ramirez-Restrepo et al. 2015), as shown below:

City structure mosaic
Fig 1. (Nilon, 2011, pg.47)

So cities have massive effects on communities of wildlife. Therefore, is it inevitable that there will be human-wildlife conflicts? Not necessarily – urban wildlife can teach children living in urban environments about the natural world (Faeth et al., 2011). Additionally, increased biodiversity is linked to sustainable development and a reduction in poverty (Nilon, 2011). So although urban wildlife may be viewed as savage scroungers surviving at the fringes of our society, they actually represent a valuable resource.

 

References

Aronson, M.F., Nilon, C.H., Lepczyk, C.A., Parker, T.S., Warren, P.S., Cilliers, S.S., Goddard, M.A., Hahs, A.K., Herzog, C., Katti, M. and La Sorte, F.A., (2016) Hierarchical filters determine community assembly of urban species pools. Ecology, 97(11), pp.2952-2963.

Faeth, S.H., Bang, C. and Saari, S., (2011) Urban biodiversity: patterns and mechanisms. Annals of the New York Academy of Sciences, 1223(1), pp.69-81.

Hobson, S. (2015) How to photograph urban wildlife, available from: http://www.discoverwildlife.com/wildlife-nature-photography/how-photograph-urban-wildlife [accessed: 15/03/17]

Nilon, C.H., (2011) Urban biodiversity and the importance of management and conservation. Landscape and ecological engineering, 7(1), pp.45-52.

Ortega-Álvarez, R. and MacGregor-Fors, I., (2009) Living in the big city: Effects of urban land-use on bird community structure, diversity, and composition. Landscape and Urban Planning, 90(3), pp.189-195.

Ramírez-Restrepo, L., Cultid-Medina, C.A. and MacGregor-Fors, I., (2015) How many butterflies are there in a city of circa half a million people?. Sustainability, 7(7), pp.8587-8597.

Sattler, T., Borcard, D., Arlettaz, R., Bontadina, F., Legendre, P., Obrist, M.K. and Moretti, M., (2010) Spider, bee, and bird communities in cities are shaped by environmental control and high stochasticity. Ecology, 91(11), pp.3343-3353.

 

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Human’s naivety towards artificial manipulation of the nitrogen cycle has devastating effects for aquatic ecosystems!

Posted on by Zac Blair

Why care about nitrogen?

natural-nitrogen
Figure 1. Growth of marine plants affected solely by natural nitrogen sources. Source: https://www.esa.org/
artificial-nitrogen
Figure 2. Growth of marine plants affected by artificial nitrogen sources, showing increased algae growth and limited oxygen availability. Source: https://www.esa.org
dead_fish0834
Figure 3. Death of trout, as a result of reduced oxygen availability. Source: http://www.edupic.net

 

 

 

 

 

 

 

 

Nitrogen ranks fourth as the most common chemical element in living tissues. Before human contribution to the nitrogen content in the atmosphere, nitrogen was a major limiting factor controlling the functioning of ecosystems (Marris, 2008)! Despite 78% of earth’s atmosphere being nitrogen, most plants and animals must wait for the nitrogen to be ‘fixed’. This occurs through its bonding with hydrogen or oxygen to form ammonium and nitrate (Fields, 2004).

The current measurement of fixed nitrogen occurs in tetragrams (Tg), which is equal to a million metric tons of nitrogen. It is estimated that the rate of natural nitrogen fixation on land is 140Tg of N per year (Vitousek et al., 1997). Surprisingly, human activities have resulted in an extra artificial nitrogen fixation of 218Tg of N per year (Vitousek et al., 1997)!

nitrogen-cycle
Figure 4. Human-driven global nitrogen changing factors have increased in a similar trend to that of the human population, except for industrial N fertilizer, which has increased at a far greater rate – growing exponentially in 1975. Source: https://www.esa.org

More worryingly is that by 2050, if predicted population trends are accurate then artificial N fixation will reach four times that of the natural production rate(Tilman & Lehman, 2001)!

Why is this important?

One of the biggest problems nitrogen poses to aquatic ecosystems, is its ability to form nitric acid through complex chemical reactions! This acid results in increasing the concentration of H+ in freshwater environments. This results in the PH of the water decreasing. A decreasing PH can result in an increase in the concentration of trace metals (Lee & Saunders, 2003). This occurs due to decreased metal sedimentation. The settling of dissolved aluminium reduces phosphate availability and therefore affects the phosphate cycle (Camargo & Alonso, 2006).

This is devastating! Phosphates are involved in the formation of ATP during respiration, and this ATP is essential for the normal functioning of an organisms metabolism, and without proper functionality, death will occur. A PH below 6 seems to be the threshold for significant damage. In fish, arrested development of embryos can occur, resulting in skeletal deformities (Camargo & Alonso, 2006).

fish-embryo
Figure 5. Zebrafish embryos at normal oxygen conditions (normoxia) and severe hypoxia conditions (anoxia), showing the developmental arrest of embryos. Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC34668

High nitrogen levels can disrupt ionic regulation, which results in molluscs, insects, fish and amphibians suffering from a deficit in calcium. This causes issues with bone development and shell maturation. In terms of the food chain, the reduced PH of aquatic environments causes a depression of net photosynthesis in planktonic and attached algae (Eisler, 2012) . This is due to the increased growth of algae which can ‘cloud’ the water preventing light penetration, as well as through disproportional oxygen consumption.

Moreover, the decline in dissolved oxygen can promote the production of hydrogen sulphide by anaerobic bacteria. Hydrogen sulphide can further reduce the availability of oxygen, due to it accumulating at the waters surface (Smith & Oseid, 1974)! This is a huge problem as dissolved oxygen is essential to the respiration of aquatic organisms, and without it, death is inevitable!

Are humans really responsible?

In short, yes, we are to blame!

table

If the current trend continues, not only will the current effects be amplified, resulting in a greater number of deaths, but the cost of aquatic organisms as a source of food will sky-rocket!

References

Camargo J, Alonso Á. (2006). Ecological and toxicological effects of inorganic nitrogen pollution in aquatic ecosystems: A global assessment. Environment International, 32(6), pp.831-849.

Eisler R. Oceanic acidification. (2012). 1st ed. Boca Raton: CRC Press

Fields S. (2004). Global Nitrogen: Cycling out of Control. Environmental Health Perspectives, 112(10), pp.556-563.

Lee M, Saunders J. (2003). Effects of pH on Metals Precipitation and Sorption: Field Bioremediation and Geochemical Modeling Approaches. Vadose Zone Journal, 2(2):, pp.77-185.

Marris, E. (2008). Nitrogen pollution stomps on biodiversity. Nature, 1, pp.1-3.

Smith L, Oseid D. (1974). Effect of Hydrogen Sulfide on Development and Survival of Eight Freshwater Fish Species. The Early Life History of Fish, 1, pp.417-430.

Tilman D, Lehman C. (2001). Human-caused environmental change: Impacts on plant diversity and evolution. Proceedings of the National Academy of Sciences, 98(10), pp.5433-5440.

Vitousek, P., Aber, J., Howarth, R., Likens, G., Matson, P., Schindler, D., Schlesinger, W. and Tilman, D. (1997). Technical Report: Human Alteration of the Global Nitrogen Cycle: Sources and Consequences. Ecological Applications, 7(3), pp.737-750

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Is Forest Fragmentation The “New” Deforestation?

Posted on by Ariadne Wilkinson
Global Forest Fragmentation is destroying our most important ecosystems.
Global Forest Fragmentation is destroying our most important ecosystems.

 

It’s a well-known fact that deforestation is happening at extreme rates! Just look at the Amazon rainforest, where 20 football pitches worth of trees are removed every minute (Carrington, 2013). These global environmental changes are associated with our topic for today: fragmentation!

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WHAT IS FRAGMENTATION?

Forest fragmentation occurs when the total cover of a native forest is reduced. It is associated with anthropogenic deforestation, and leads to patchy forests and overall forest loss (Murcia, 1995) (Kupfer et al, 2006).

The isolated patches of forested habitats (remnants) in between the cleared forest cover follow the theory of ‘Island Biogeography’. Principles of Island Biogeography link forest fragmentation with biodiversity loss (Kupfer et al, 2006).

This is a good representation of forest fragmentation by Bacles & Jump (2011). The remnants have a drastically different ecosystem than their surroundings, just like an Island’s ecosystem is isolated from the outside world.
This is a good representation of forest fragmentation by Bacles & Jump (2011). The remnants have a drastically different ecosystem than their surroundings, just like an Island’s ecosystem is isolated from the outside world.

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FRAGMENTATION EFFECTS ON ECOSYSTEMS

 

– Microclimate Change (Saunders et al, 1991)

The microclimate within and surrounding the remnant forest is altered in the following ways:

More solar radiation. This restricts shade-tolerant species and encourages the spread of new species of plants (ex. vines, secondary vegetation) and animals to occupy the forest clearings and edges.

The accompanied temperature rise alters soil moisture and nutrient availability, modifying the local vegetation. It also disturbs species interactions and animal foraging behaviours (ex. Carnaby’s cockatoos).

Image by Georgina Steytler: A Carnaby’s Black-Cockatoo (Calyptorbynchus funereus latirostrus). Higher temperatures in fragmented cockatoo habitats reduced their foraging time available, which led to their local extinction in areas of Western Australia (Saunders et al, 1991)
Image by Georgina Steytler: A Carnaby’s Black-Cockatoo (Calyptorbynchus funereus latirostrus). Higher temperatures in fragmented cockatoo habitats reduced their foraging time available, which led to their local extinction in areas of Western Australia (Saunders et al, 1991).

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Stronger winds. Reducing the denseness of the forest leaves it more exposed to penetrating winds. That, amongst other things, changes vegetation structures and food availability for the forest communities.

Increased water flux. Fragmented forests alter the landscape through heavy water flows that erode the topsoil and transport more particulate matter across the forest cover.

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– Isolation (Saunders et al, 1991)

Remnant forest habitats are usually left crowded, with more species than they can actually support. Therefore, over time species will inevitably be lost due to the lack of resources and space available.

Species survival will generally depend on how well they can adapt to new conditions or migrate to new areas. The most rapid extinctions will occur for species with small populations, or ones that are heavily dependent on native vegetation or large territories.

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– Greenhouse Effect

Tropical rainforests store large amounts of carbon. Destroying them releases this stored carbon into the atmosphere and largely contributes to global warming (Laurance et al, 2002).

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MADAGASCAR

Fragmentation is a serious issue for this biodiversity hotspot, and its all due to human activities.

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Fragmentation is a major concern for Madagascar: The original extent of the eastern rainforest was around 3 times larger than what it currently is!

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Prior to human colonisation the forest on the eastern highland spine of Madagascar was 11.2 million ha, but by 1985 it only covered 3.8 million ha (Green & Sussman, 1990). (These satellite images can be found in Conservation Corridor).

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Its size is diminishing due to fires, illegal logging and agricultural deforestation (Ganzhorn et al, 2001).

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The forest on the Eastern Highland spine of the island is shrinking very fast. Forest can only survive within the gullies, where the fires can’t reach it. Image by: Josia Razafindramanana.
The forest on the Eastern Highland spine of the island is shrinking very fast. Forest can only survive within the gullies, where the fires can’t reach it. Image by: Josia Razafindramanana.

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Many larger species have been lost, and the remainder are unlikely to maintain viable populations beyond 2040. Populations of lemurs with fewer than 40 adults cannot survive. Worryingly, none of the remnant patches on the eastern Madagascar forest are large enough to maintain even such populations (Ganzhorn et al, 2001).

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Lemurs are holding on to the trees for dear life. The high rate of fragmentation is a major concern for these primates, as well as for all of Madagascar’s endemic forest ecosystems. Image by Frank Vassen
Lemurs are holding on to the trees for dear life. The high rate of fragmentation is a major concern for these primates, as well as for all of Madagascar’s endemic forest ecosystems. Image by Frank Vassen.

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THE ONLY SAVING GRACE: CONNECTIVITY

Corridors to connect remnants have proven useful when striving to enhance biodiversity.

They can aid the re-colonisation and immigration of species, provide refuge, and help with further species interactions (Saunders et al, 1991) (Laurance et al, 2002).

The size and shape of the remnants can also affect its vulnerability to external factors:

The best conditions for the conservation management of the ecosystems within remnant patches or forest (here they are termed ‘reserves’ from the “Island-like reserves” biogeography theory) can be seen in this image. The theory of forest connectivity is linked to this.

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Word Count: 499

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FOR MORE INFORMATION ON:

Fragmentation effects on ecosystems you can watch: https://www.youtube.com/watch?v=lzf-uX6kGkk

How Madagascar is managing its lemur populations you can watch: https://www.youtube.com/watch?v=ZhOyD79ymJA

 

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REFERENCES:          

          Carrington, D. (2013). Amazon deforestation increased by one-third in past year. [online] the Guardian. Available at: https://www.theguardian.com/environment/2013/nov/15/amazon-deforestation-increased-one-third [Accessed 18 Mar. 2017].

          Ganzhorn, J., Lowry, P., Schatz, G. and Sommer, S. (2001). The biodiversity of Madagascar: one of the world’s hottest hotspots on its way out. Oryx, 35(04), p.346.

          Green, G. and Sussman, R. (1990). Deforestation History of the Eastern Rain Forests of Madagascar from Satellite Images. Science, 248(4952), pp.212-215.

          Kupfer, J., Malanson, G. and Franklin, S. (2006). Not seeing the ocean for the islands: the mediating influence of matrix-based processes on forest fragmentation effects. Global Ecology and Biogeography, 15(1), pp.8-20.

          Laurance, W., Lovejoy, T., Vasconcelos, H., Bruna, E., Didham, R., Stouffer, P., Gascon, C., Bierregaard, R., Laurance, S. and Sampaio, E. (2002). Ecosystem Decay of Amazonian Forest Fragments: a 22-Year Investigation. Conservation Biology, 16(3), pp.605-618.

          Murcia, C. (1995). Edge effects in fragmented forests: implications for conservation. Trends in Ecology & Evolution, 10(2), pp.58-62.

          SAUNDERS, D., HOBBS, R. and MARGULES, C. (1991). Biological Consequences of Ecosystem Fragmentation: A Review. Conservation Biology, 5(1), pp.18-32.

 

 



Caring for the Community – How Climate Change is Impacting You!

Posted on by Kirsty State

Global warming has resulted in many species responding and behaving differently.  These changes can impact communities of plants, animals, people, in fact, all species that interact with each other within an environment.

Responses by different species to climate change are all connected through the interactions and shared resources of an ecosystem.  Overall earlier life events, such as flowering, feeding and hatching, are being recorded (Walther, 2010).  However, species do not respond equally to environmental changes.  This can result in timings of species interactions being off as a result of varying degrees of responses to temperature changes

The species found at certain locations are determined by three “filters”:

  • Dispersal
  • Environmental
  • Interactions

These filters are based around interacting species and their tolerance to specific environmental conditions (Götzenberger et al., 2012).  Global warming can be seen as an environmental filter (Weiher et al., 1998).  The increase in temperature could result in species being more or less tolerant of the increased temperature and therefore could change the collection of species in a community.

Climate change is occurring all over the planet, with certain ecosystems being particularly sensitive to it…

Take, for example, the tundra.  This is the area that borders the arctic, where species have to adapt to low temperatures with high variation.  Warming can result in many changes in this area.  Evidence from Alaska shows that climate change can influence land cover (Hinzman et al., 2005). This is through the increasingly more temperate climate, which allows species to grow in less hostile areas which were previously too cold or dry.

rein

Reindeer herd moving across their snowy calving grounds in the Mackenzie Delta, Canada (Dory, n.d)

Reindeer and Caribou species have been increasing in number in northern latitudes.  These play an important role in communities as they are often the largest, most numerous herbivores in an area.  As seen in the diagram below, the species are both affected by climate change impacts on the ecosystem as well as changing the ecosystem themselves.  Their impact on the environment has the potential to cause a vegetation transition (Bernes et al., 2015).  This could result in a knock on effect to other species that also feed off the vegetation eaten by Reindeer and Caribou.

flow-diagram

Flow diagram showing how increased temperatures affects vegetation and large herbivores

Another example is the plant-pollinator relationship that is disrupted by increasing temperature.  Both pollinators and the plants they pollinate, are changing their feeding and flowering times, respectively, at similar rates.  However, these rates are not exactly equal, resulting in a mismatch in the timings (Hegland et al., 2009).  Consequences of this mismatch are that pollination is not as efficient as it could be and that both plant and pollinators numbers are at risk.  This can have bottom up effect on the ecosystem, especially on species (such as humans) that rely on crops that are pollinated as a source of food (Walther, 2010).

bee-and-flower

Bumblebee pollinating a Dahlia ‘Moonfire’ plant (Photo by Kirsty State, 2015).

From these case studies it is important to note that not only is climate change impacting specific species that respond to temperature change, but through a network of communities and interactions within an ecosystem, it can indirectly affect us all.

 

 

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References

Bernes, C., Bråthen, K.A., Forbes, B.C., Speed, J.D. and Moen, J., 2015. What are the impacts of reindeer/caribou (Rangifer tarandus L.) on arctic and alpine vegetation? A systematic review. Environmental Evidence, 4(1), p.1-26.

Dory, N., n.d.  The reindeer of the Mackenzie Delta, Northwest Territories. [photograph] Available at: <http://www.nicolasdory.com/reindeer-of-the-mackenzie-delta/> [Accessed 17 March 2017].

Götzenberger, L., de Bello, F., Bråthen, K.A., Davison, J., Dubuis, A., Guisan, A., Lepš, J., Lindborg, R., Moora, M., Pärtel, M. and Pellissier, L., 2012. Ecological assembly rules in plant communities—approaches, patterns and prospects. Biological reviews, 87(1), pp.111-127.

Hegland, S.J., Nielsen, A., Lázaro, A., Bjerknes, A.L. and Totland, Ø., 2009. How does climate warming affect plant‐pollinator interactions? Ecology letters, 12(2), pp.184-195.

Hinzman, L.D., Bettez, N.D., Bolton, W.R., Chapin, F.S., Dyurgerov, M.B., Fastie, C.L., Griffith, B., Hollister, R.D., Hope, A., Huntington, H.P. and Jensen, A.M., 2005. Evidence and implications of recent climate change in northern Alaska and other arctic regions. Climatic Change, 72(3), pp.251-298.

Walther, G.R., 2010. Community and ecosystem responses to recent climate change. Philosophical Transactions of the Royal Society B: Biological Sciences, 365(1549), pp.2019-2024.

Weiher, E., Clarke, G.P. and Keddy, P.A., 1998. Community assembly rules, morphological dispersion, and the coexistence of plant species. Oikos, 81(2), pp.309-322.



Addressing the Elephant in the Room: A look into the Global Loss of Megafauna

Posted on by Julia Daly

In the light of the current epoch, the Anthropocene, being classified as a sixth mass extinction (Pievani, 2014), losses in biodiversity and its effects on ecosystems, from which humans directly benefit, has had a lot of scientific attention (Diaz et al., 2006). However, only recently has there been a focus on the global loss of terrestrial megafauna; larger bodied mammals of mass greater than 1000kgs (Ripple et al., 2015). In March 2014, the University of Oxford hosted the first ever international conference on ‘Megafauna and Ecosystem Functions’ (Malhi and Doughty, 2015) to address this global issue. Terrestrial megafauna, are under threat from human caused habitat loss and fragmentation (Segan et al., 2016), due to land-use change, such as agricultural expansion and deforestation (Ripple et al., 2015, 2016). Although this is a global issue, the heaviest decline in megafauna is concentrated in sub-saharan African and south-east Asia (Figure 1).

screen-shot-2017-03-21-at-23-27-08

 

Figure 1– Global representation of the number of declining megafauna worldwide (Ripple et al., 2016)

Environmental change through the alteration of habitats puts the larger sized megafauna at a higher risk of extinction as they need larger, non-fragmented habitats, and have slower life-histories (Ripple et al., 2016), taking longer to reproduce.

Why focus on megafauna? Extensive research into losses of biodiversity and its effect on ecosystems has revealed one thing for certain: the importance of functional traits. Biodiversity can ensure the functioning of an ecosystem if its functional composition is adequate to maintain the system, having organisms with specific traits (Diaz, et al., 2006). Much like a well-working machine, all the pieces are needed for it to run. The more important parts of this machine, or ecosystem, are the megafauna, as many act as ecosystem engineers (Smith et al., 2015) and keystone species (Ripple et al, 2016). Megafauna fill the roles- niches- in the ecosystem that would otherwise not be filled. The effect of their loss will be felt by the whole ecosystem as impacts will filter down through trophic levels and the food web (Svenning et al., 2015).

The African elephant alters ecosystem structure and composition, through various behaviour including uprooting and debarking of trees (Mograbi et al., 2017), seed dispersal and alteration of habitats (Ripple et al, 2015). They have overall effects on the ecosystem in which they live, which indirectly affects the other organisms that depend on that ecosystem (Figure 2). Land-use change has caused a decline in African elephants (Ripple et al., 2015); a key player in ecosystem functioning. The ecosystem may therefore begin to fall apart without it’s key piece (Smith et al., 2015). This is just one example of how the loss of a single species can have significant implications, highlighting the severity of impacts if several species were to be lost.

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Figure 2– Diagram demonstrating how the African elephant can effect the ecosystem and the other organisms they impact (Ripple, et al., 2015).

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Figure 3 – Diagram and explanation of the interactions between global changes, human activities and ecosystems (Chapin III, et al., 2000).

These global changes can be felt not only by the animals, that depend on the megafauna, but by humans as well. Figure 3 shows how humans will also ultimately feel the effects of the global changes they cause due to their effects on ecosystems.

 

 

References:

Chapin III, F. S., Zavaleta, E. S., Eviner, V. T., Naylor, R. L., Vitousek, P. M., Reynolds, H. L., Hooper, D. U., Lavorel, S., Sala, O. E., Hobbie, S. E., Mack, M. C., Diaz, S., 2000. Consequesnce of changing biodiversity. Nature 405, pp 234-242.

Diaz, S., Fargione, J., Chapin III, F. S., Tilman, D., 2006. Biodiversity Loss Threatens Human Well-Being. PLoS Biol 4(8): e277

Malhi and Doughty, 2015. Megafauana and Ecosytem Function: Learning from the Giants. Available at < http://www.eci.ox.ac.uk/news/2015/1026-megafauna.html> [Accessed: 21st March 2017]

Morgabi, P., Asner, G. P., Witkowski, E. T. F., Erasmus, B. F. N., Wessels, K. J., Mathieu, R., Vaughn, N. R., 2017. Humans and elephants as treefall drivers in African savannas. Ecography 40: 001-011

Pievani, T., 2014. The sixth mass extincton: Anthropocene and the human impact on biodiversity. Rend. Fis. Acc. Lincei 25: 85-93

Ripple, W. J., Newsome, T. M., Wolf, C., Dirzo, R., Eceratt, K. T., Galetti, M., Hayward, M. W., Kerley, G.I.H., Levi T., Lindsey, P. A., Macdonald, D. W., Malhi, Y., Painter, L. E., Sandom, C. J., Terborgh, J & Van Valkenburgh, B, 2015. Collapse of the world’s largest herbivores. Science Advances, 1: e1400103, pp 1-12

Ripple, W. J., Chapron, G., López-Bao, J. V., Durant, S. M., Macdonald, D. W., Lindsey, P. A., Bennett, E. L., Beschta, R. L., Bruskotter, J. T., Campos-Arceiz, A., Corlett, R. T., Darimont, C. T., Dickman, A. J., Dirzo, R., Dublin, H. T., Estes, J. A., Everatt, K. T., Galetti, M., Goswami, V. R., Hayward, M. W., Hedges, S., Hoffmann, M., Hunter, L. T. B., Kerley, G. I. H., Letnic, M., Levi, T., Maisels, F., Morrison, J. C., Nelson, M. P., Newsome, T. M., Painter, L., Pringle, R. M., Sandom, C. J., Terborgh, J., Treves, A., Van Valkenburgh, B., Vucetich, J. A., Wirsing, A. J., Wallach, A. D., Wolf, C., Woodroffe, R., Young, H. and Zhang, L., 2016. Saving the World’s Terrestrial Megafauna. BioScience, 60 : 10, pp 807-812

Segan, D., B, Murray, K. A., Watson, J. E. M., 2016. A global assessment of current and future biodiversity vulnerability to habitat loss-climate change interactions. Global Ecology and Conservation 5, pp 12-21

Smith, F. A., Doughty, C. E., Malhi, Y., Svenning, J., Terborgh, J., 2015. Megafauna in the Earth System. Ecography 39: 2, pp 99-108

Svenning et al., 2015. Science for a wilder Anthropocene: Synthesis and future directions for trophic rewilding research. PNAS 114 (4), pp 898-906

 

 

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