Humans, Freshwater, Species

Endangered Coahuilan box turtle in Mexico

Previously, I talked about habitat loss of species. Little do we know, freshwater is facing greater pressure from humans and extinction is fast approaching freshwater species..

"Massive mismanagement and growing human needs for water are causing freshwater ecosystems to collapse, making freshwater species the most threatened on Earth. Extinction rates for freshwater species including fish, frogs, crocodiles and turtles were four to six times higher than their terrestrial and marine cousins." - Diversitas, an international group of biodiversity experts 

It is not beyond imagination that human source of threats are not restricted within habitat loss. Dudgeon and his team suggested that impact posed by humans consist of five main categories:

Five major categories on freshwater biodiversity

The impact of human on freshwater is interrelated with their other influences, as demonstrated above. Pollution is one of the most serious problems. Water pollution from domestic and industrial sources leads to excessive nutrient enrichment and the growth of other chemicals like endocrine disrupters. This chemical will cause disturbance to the hormone systems of species. Hence, it leads to possible depletion of species. Habitat alterations such as forest clearance, as mentioned previously, can change the surrounding of the homeland of species. For instance, it will increase river sediment loads and lead to shoreline erosion. The disproportionate water distribution for plants and animals (Surface freshwater habitats contain only 0.01% of world's water but are housing 40% of global fish diversity and 25% of global vertebrate diversity), together with the other harmful effects brought by humans, make freshwater species highly vulnerable to extinction. 

Not convinced?

The edge of extinction is actually highly visible in many places, where a lot of freshwater species are now endangered due to disturbance from humans. In Spain, record of threatened freshwater fish can be dated back from 1986.  

Percentages of endangered freshwater fish in Spain
Ex?: Probably extinct, E: endangers, V: vulnerable, R: rare, I: indeterminate, K: insufficiently known, NT: not threatened 

Unthreatened species significantly decreased. In 1992, there was 1% of freshwater fish at the edge of extinction. Amount of rare species raised 7%, including Hucho hucho, Salelinus fontinalis and Ictalurus melas. 

Hucho hucho

Salvelinus fontinalis

Ictalurus melas

Human, not surprisingly have played a crucial role in effecting the endangered fish. Construction of 11, 000 large dams in Spanish rivers has jeopardised survival of migratory species. These dams also led to significant loss of habitat with establishments of large reservoirs, water-flow regulation and water withdrawal. 

Here's a quick summary: Freshwater habitat, contains the most endangered species. They are highly affected by human activity and modification to the surroundings. There were already 20% of freshwater species that had gone extinct. Given the limitation on research in vast freshwater species, it is likely that more than that are close to extinction. Have people thought about the consequences before building dams and clearing forests?

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.. 

Humans' Alteration of Nature

In my previous blogs, I have mainly investigated the contributions by climate change to extinction. As my ultimate goal is to find out whether we are on the edge of the sixth extinction, I also investigated other factors; specifically, I researched into the impact on species that is currentlycaused by humans. 

Peter M. Vitousek and his colleagues produced an influential paper on this topic. I find this diagram they created very useful in terms of understanding the contribution by humans to possible environmental changes. Inevitably, humans modify the environment to make possible their developmental plans. Figure 1 is a good summary of the impacts of human actions. 

Instead of summarising the paper, I will talk about land and ocean alterations, as they interest me the most. It is certainly not surprising that land transformation represents the primary driving force in the loss of worldwide biological diversity. There is an extreme case of land alteration, up to 10-15% of Earth's land surface transformed for agriculture or urban-industrial development. Deforestation is one of many reasons behind habitat loss. According to the research conducted by FAO, global deforestation rate has accelerated since 1980. For instance, habitat alterations in the two Brazilian tropical rain forest biomes, Amazonian and Atlantic have led to the alteration of local and regional biodiversity - possibly leading to extinction. Not to mention how land alteration affects climate by directly contributing ~20% to current anthropogenic carbon emissions..

Sumatran elephants are one of the victims of such alteration. The species is now critically endangered, half of its population disappeared, as they experienced one of the highest rate of deforestation in Asia. As natural lowland forest has razed in the past 25 years, nearly 70% of their habit have been destroyed in one generation. 

Humans have been affecting the productive coastal margins in oceans too. This has significant impact, as coastal wetlands are responsible for mediating interactions between land and sea. Approximately 50% of mangrove ecosystems have been transformed or destroyed by human activity globally. Together with unsustainable practices of fishermen, fish that are over-exploited could float towards the edge of extinction. 

Despite all the negative views on human activities, some reckon that actions of humankind can increase genetic diversity through resource alteration and new selective pressures. Moreover, conservation schemes have been implemented to protect endangered species. One quarter of the Brazilian Amazon forests is under effective conservation regimes, up to 70% will be expected to be maintained. Recently, Scottish wildcats are under a new conservation strategy that aim to save them from extinction.

Conservation policies appear, but human development continues. Without doubts wide range of species are still experiencing threats from the human population. 

People, Climate Change and Extinction

The majority of geographers are comfortable with the concepts of climate change, but it is still worth listening to James Hansen, who spoke about greenhouse effects and its possible impacts. He stated that IPCC estimated 20-50% of all species would be ticketed to extinction by the end of the century, assuming that we maintained our current rate of consumption in fossil fuels. But for those who already have a clear idea of all the long-winded theories of climate change, PLEASE watch the following (if you only have a few minutes, start from 9:48) :

Lewis Pugh, did something amazing to raise the awareness of the need to mitigate climate change. His dream to travel to the North Pole has led to our, or at the very least, my realisation of what we are about to lose - "Watching those polar bears walking on thin ice, they might be gone in few years time". 

It is clear that human activity is the major cause of climate change. Our unsustainable use of non renewable resources might have started to slowly destroy our own beautiful Earth long ago. 

Many scientists and geographers have been engaging in research on this matter - humans inducing climate change, that in turn leads to destructive impact on species. Thomas and his team claimed that at the highest expected rate of climate change, 58% of species are expected to become extinct if there is no dispersal. On the other side of the coin, there will be To the least, 11% of species becoming extinct at the lowest expected rate of climate change. There is evidence of Coral Reef extinction due to global warming as well. Thomas and his colleagues have definitely raised this issue into concern. Questions have been raised - How great will the impact be? Is it just another natural process in the ecosystem?

Addressing the second question, I would say given the rate of possible extinction, it is just not natural. In some places, climate change has become the biggest threat along habitat destruction. Statistically, under minimum climate scenarios, montane Queensland forests would experience 7-13% extinction, but on the basis of habitat destruction only (within the rates allowed by the law) but not climate change, the percentage would be 0%. Although I suggested the direct link of climate change and extinction, human is the indirect cause towards the edge of extinction. After all, human development, industrial revolution and consumption of fossil fuels are the overriding reasons for climate change.

On another note, hope everyone is having a good and productive reading week! 
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