Habitat Fragmentation

Monday's blue - Yes, species have been losing their homeland!

In the previous blog, I mentioned how humans have been altering landscapes and hence have impacted livelihood of many species. Today, I would like to examine further into this area - extinction due to the loss of homeland. Without doubt, human developed at the expense of nature. Bennet and Saunders argued that the destruction and fragmentation of habitats are major factors in decline of populations of species. Southeast Asia had one of the highest loss of species in mammal population extensions: 57% of its quadrants have lost between 75-100% of their mammals.

First of all, habitat fragmentation is the dismantling of continuous habitat, such as tropical forest. resting in three phenomena. 

1. Habitat loss
2. Subdivision of the remaining vegetation - Habitat fragmentation
3. Replacement of vegetation 

Although the third situation might be favourable to species, the initial removal of large tracts of native vegetation would have already modified physical processes and the environment. Say, cleared land would have different humidity, ground and air temperature and wind speed compared to forests. Even with the replacement of vegetation, it is close to impossible to create a perfect resemblance of the previous habitat. In addition to the time gap until the replacements, species may evolve, migrate, or decline in populations. 

Lemuroid ringtail possum - also known as Lemur-like ringtail possum

Rainforest fragments are found in Queensland, Australia. A research found that with time lag, species richness in fragments declined further from 1986. As a result, by 2006-7, the lemuroid ringtail possum has become an endangered species.

Evidently, the loss of species in 2006 (open circles) was more serious compared to that of 1986 (filled circles). 

There are, however, some species that have higher tolerance for human disturbance, such as Spotted hyena. Despite this attribute, the population of Spotted hyena also lost 14%. 

Spotted hyena - also know as Laughing Hyena

Extinctions today concentrated either in areas of high human population densities, or places where human activities dominant. Southeast Asia is one of the examples - human population density is extremely high. Countries such as China and India are countries that have the  highest populations in the world. 

Southeast Asia
Left to right: Historic number of species with populations in each 2 x 2 quadrate,  number of species lost from each quadrate, percentage of species that have disappeared from each quadrate 

North America
Left to right: Historic number of species with populations in each 2 x 2 quadrate,  number of species lost from each quadrate, percentage of species that have disappeared from each quadrate 

Lost species concentrated within the categories of 5-6 and 7-8, where populations were high. Similarly, North America had the highest percentage losses in the heavily populated eastern United States. 

Summarising the above, as humans have been removing forests to build skyscrapers, species are forced to leave their homes. As they fail to adapt to new environments, extinction will be inevitable. The question will again be: What's next? Development is unstoppable, and there are little escape routes for species..