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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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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.