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Tag: deforestation

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



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.

 

 



Roads Reduce Role of Rainforests

Posted on by Anonymous

Rainforests are considered ‘the finest celebration of nature ever known on the planet’ yet increasing pressure to develop new roads for economic growth is their biggest threat.

Tropical rainforests cover 2-7% of Earth. They support 170,000 plant species. Their small area but tremendous biodiversity makes them global hotspots for conservation funds.

High levels of rainfall and constantly high temperatures creates a unique habitat. Many trees packed closely together creates a closed canopy. As a result, the rainforest is dark and humid. There is lower light, wind and temperatures as a result that species need to be specially adapted to in order to thrive (Laurance et al. 2009).

New developments threaten this structure. Species can either respond and adapt to new conditions or face the risk of extinction.

Rainforests are especially vulnerable to economic pressures. Roughly 2.5 million hectares (25,000km2) of the Brazilian Amazon are lost every year through deforestation. Economic growth is often the main driver for habitat loss. If the current rates continue, within 50 years, global rainforests are likely to be lost forever.

Many activities lead to deforestation but roads are seen as especially detrimental (Figure 1). Opportunities for logging, oil and mining often drive the development of new roads (Goosem 2007). Previously untouched areas are now accessible via roads and are now vulnerable to widespread biodiversity loss (Brudvig et al. 2015; Haddad et al. 2015).

Figure 1. New roads create barriers between previously connected species. Barriers for reproduction and pollination ultimately lead to species loss.
Figure 1. New roads create barriers between previously connected species. Barriers for reproduction and pollination ultimately lead to species loss.

The issue is not only minor access roads but large highways built for an increasingly urban world. The Trans-Amazonian Highway in Brazil is 4000km. This only makes it the third longest highway in Brazil (Figure 2).

Destruction of the rainforest is therefore a primary cause of plant biodiversity loss. Roads will change rainforest habitats from large and pristine to small and isolated. New edges are created alongside roads. Species are impacted more than this than widespread deforestation. This process of habitat fragmentation creates smaller, isolated populations and plant species are lost (Linert 2004; Gossem et al. 2011; Weiner et al. 2014).

Figure 2. Trans-Amazonian Highway is among one of many road developments through tropical rainforests that result in widespread deforestation and loss of important plant species that play vital roles in regulating carbon dioxide levels on Earth.
Figure 2. Trans-Amazonian Highway is among one of many road developments through tropical rainforests that result in widespread deforestation and loss of important plant species that play vital roles in regulating carbon dioxide levels on Earth.

Overall, trees lost from the rainforest allows light to reach the ground that was not able to before. Shade preferring species are no longer the best suited. Those plants that thrive on more light become more successful (Laurance et al. 2009). Species that were one dominant no longer are.

These changes to the surrounding environment impact important interacting species. Smaller patches with different conditions attract fewer plant species and therefore fewer pollinators. Pollinating species are likely to decline as a result, threatening their own survival and that of the plants (Aguilar et al. 2006).

If reproductive output declines, the number of species surviving to continue the population declines. The negative cycle continues until a whole species is extinct. Community structure is altered and important interactions are lost.

Each plant species, rare or common, plays an important role in regulating carbon, purifying water and stabilising soil qualities. Loss of species variety creates areas that are extremely similar. Soon, rainforests will lose their functional role and contribute less to the global system.

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REFERENCES

Aguilar, R., Ashworth, L., Galetto, L. & Aizen, M. A. (2006) Plant reproductive susceptibility to habitat fragmentation: review and synthesis through a meta-analysis. Ecology Letters, 9, 968-980.

Brudvig, L. A., Damschen, E. I., Haddad, N. M., Levey, D. J. & Tewksbury, J. J. (2015) The influence of habitat fragmentation on multiple plant-animal interactions and plant reproduction. Ecology, 96, 2669-2678.

Cunningham, S. A. (2000) Effects of habitat fragmentation on the reproductive ecology of four plant species in mallee woodland. Conservation Biology, 14, 758-768.

Goosem, M. (2007) Fragmentation impacts caused by roads through rainforests. Current Science, 93, 1587-1595.

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. A. & Townshend, J. R. (2015) Habitat fragmentation and its lasting impact on Earth’s ecosystems. Sci. Adv.

Laurance, W. F., Goosem, M. & Laurance, S. G. W. (2009) Impacts of roads and linear clearings on tropical forests. TREE, 1149, 1-11.

Lienert, J. (2004) Habitat fragmentation effects on fitness of plant populations – a review. Journal for Nature Conservation, 12, 53-72.

Weiner, C. N., Werner, M., Linsenmair, K. E. & Bluthgen, N. (2014) Land-use impacts on plant-pollinator networks: interaction strength and specialisation predict pollinator declines. Ecology, 95, 466-474.