There has been debate over the present day characteristics of biomes of tropical regions. For some, they are seen as a natural response to the climate of the area, whereas for others they are regarded as a product of human interference.
Discuss the statement in the context of the tropical biome you have studied. [40]
A tropical rainforest is an ecosystem type that occurs roughly within the latitudes 28 degrees north or south of the equator (in the equatorial zone between the Tropic of Cancer and Tropic of Capricorn). This ecosystem experiences high average temperatures and a significant amount of rainfall. In particular, I will be focusing on Borneo Rainforest, which is the oldest rainforest in the world. The island is divided among three countries (figure 1): Malaysia and Brunei in the north, and Indonesia to the south. Approximately 73% of the island is Indonesian territory. In the north, the East Malaysian states of Sabah and Sarawak make up about 26% of the island. Climate is the average weather the region receives over a 30 year period. Climate can be on a global scale or a local scale, for instance where it is mountainous more rainfall is generated therefore that region sees a different climate to perhaps a neighbouring region. Aspect and altitude also affects climate, which will be explored in greater detail.
The purpose of this essay is to explore whether the natural, climatic factors have influenced the characteristics of the rainforest, or whether humans have had an influence on it. I will be focusing in the current day characteristics to start off with, and after establishing these I will then describe the climatic responses and human responses, to see how they relate to the characteristics evident. I will then bring my findings together and conclude both the ecocentric and technocentric views and comment on which I find more influential on the characteristics.
There are many characteristics of tropic rainforests present today. The rainforest has a clear structure (figure 2), with an upper canopy of 40m which lies beneath emerging trees which can reach 50m tall. The is then a lower canopy which reaches 20m, and beneath that at 5m is the lower shrub canopy. This structure means that only 2% of the sunlight can reach the ground floor, which is a significant climatic factor influencing the rainforest. Due to this small sunlight available, fauna and flora have to be specially adapted. In particular, the plants must adapt, as they need sunlight to photosynthesise. Climbing plants are found on trees of the forest, as the coil and climb up large, upper canopy and emergent trees to reach sunlight which is not sufficient at the forest floor. Lianas are an example of these, as their thick, twisted vines loop around trunks, which can be up to 100m long. Epiphytes are also adapted to living at the top of the canopy, as they grow on tree branches and don’t need to have their roots planted in soil. As dead leaves from the canopy above them fall off, the epiphytes catch them and as they decay nutrients are added to the plants. The height of the trees is also influenced by climate, as the trees receive sunlight and rainfall therefore can reach a maximum height of 50m. The forest receives 12 hours on sunlight every day, and an average of 2000mm of rainfall annually. In Borneo, 95% of the rain is generated by the forest. This local climate has a knock on effect to the forest.
The high rainfall can leach the nutrients out of the soil. This would help explain why the roots of plants and trees are near to the surface of the soil, as if they were any further down the soil would be nutrient deficient. Buttress roots are another characteristic seen in the biome of the tropical rainforest, where the large, wide roots support the heavy trees. The plant adaptations allow them to cope with the climatic conditions, which is evident through the thick, waxy leaves that trees have. These prevent rotting, and allow water to just run down the surface without damaging the leaf. The leaves often have drip-tips (figure 3), which allow them to shed the water. This adaptation enables plants to cope with the heavy rainfall.
Not just plant adaptations indicate the characteristics on rainforests are natural responses to climate, but so are animal adaptations. The specialisations occur as a natural response to the areas climate. For instance, algae can grow on the Three Toed Sloth, giving it camouflage in the forest. This algae is enabled to grow on fur due to climatic conditions, making it possible for the sloth to be disguised in their habitat. The climate has also enabled specialised butterflies to grow, for instance the Monarch Butterfly. This poisonous butterfly hatches from the Monarch caterpillar, which feeds off the Milkweed plants. These plants are highly poisonous and release a latex which engulfs 2/3 of the caterpillars, however once they develop in butterflies, they are poisonous predators who are able to feed off the Milkweed flowers. It is due to the climatic conditions which have enabled these specialised plants and animals to grow and develop, which has influenced the characteristics of the present day biome.
The fauna of the rainforest is one of the most diverse ecosystems in the world. Borneo is estimated to be home to around 222 mammals (including 44 endemic – meaning they are not found anywhere else in the world), 420 birds (37 endemic), 100 amphibians and 394 fish (19 endemic). Borneo’s tropical rainforests and climate provide the ideal conditions for a wide variety of species to thrive. Dipterocarp trees hold the greatest insect diversity on Borneo - as many as 1,000 species can be found in just 1 tree.
It also seems likely that the rainforest has gone through many cycles of fragmentation and reunion, due to the same global climate changes that gave us repeated bouts of glaciations at higher latitudes. These repeated episodes of forest retreat and advance would provide numerous opportunities for forest-dwelling species to be isolated into separate small populations. This in turn allows genetic change and evolutionary specialization to occur. During periods of glaciation, the earth's average temperature was cooler, and this would result in less evaporation and thus less rainfall. During these dry periods, the area receiving more than 1500 mm of rainfall would be reduced and fragmented.
During wetter periods associated with interglacials (time during the glacial retreats), forests would expand. If the dry periods correspond roughly to periods of glacial advance, they would have lasted 50 to 100 thousand years, which likely is sufficient time for evolutionary divergence. This process has happened over and over, in conjunction with the many cycles of glaciation that the earth has experienced in the last several million years. Therefore the Milankovitch Cycle comes in to play, as the glacial activity may have acted as a ‘species pump’, causing the process of speciation to be more active in tropics and resulting in the wide diversity of species found today. This temporal scale helps explain why the species are so diverse in the forest at Borneo.
Climate has had a knock on effect to the characteristics of the rainforest on several different scales, in particular spatial and temporal scales. Spatial scale looks at the distance and size, and temporal scale concentrates on time. The climate of the rainforest is local to an extent, as most of the rainfall is generated by the rainforest alone. Rainfall tends to be highest near the equator, where the sun's evaporative power causes high evapotranspiration, and rising air cools and then sheds its moisture. Precipitation tapers off as one moves away from the equator, and dry belts are found at 25-30 degree of latitude. Local variation can also be great due to trade winds, ocean currents, land masses, and mountain ranges. Similarly to rainforests, the tropical biomes of coral reefs also require certain conditions to grow. No reefs develop where the mean annual temperature of water is below 18oC. However, above 21oC causes problems of health to the reef. The Maldives coral reefs fit this temperature requirement as its temperature never exceeds these extremes.
Due to this climate, evergreen forests are replaced by deciduous forests as precipitation becomes seasonal. Wherever dry periods are several months or longer in duration, leaves are shed as the dry season takes hold, providing a winter-like visual appearance. Leaves re-appear in anticipation of or with the onset of the rains. (A dry month is one where evapotranspiration exceeds precipitation.) The growing season is thus shortened, and so forest productivity is less than in the evergreen forests of the more humid tropics.
Human interference is a key part of both the spatial and temporal scales that are seen at the tropical biome. Spatially, humans exploit large areas of the rainforest at Borneo, for uses for as logging, cattle ranching and hydro-electric power. In some places, the exploitation is lower than others, and is other places the human interference may have less impact on the forest. On a temporal scale, the result of the rainforest under human influences has dramatically risen in the last decade or so, as new technologies and modes of transport are accessible for humans to exploit and use the land.
Deforestation (figure 4) is a key characteristic of the tropic biome in Borneo. Deforestation is the process by which natural forests are removed through burning or logging, either to use as timber or replace the area with an alternative use. Illegal logging has become a way of life for some communities, with timber being taken from wherever it is accessible, sold to collectors and processed in huge sawmills. In the absence of sufficient alternative economic development, this is an irresistible lure for the local communities.
Satellite studies show that some 56% of protected lowland tropical rainforests in Kalimantan were cut down between 1985 and 2001 to supply global timber demand – which is more than 29,000 km² (almost the size of Belgium). One of the biggest drivers of deforestation in the Heart of Borneo and Kalimantan is the growth of oil palm plantations in response to global demand for palm oil, the most important tropical vegetable oil in the global oils and fats industry. Within Indonesia, oil palm production expanded from 600,000 hectares in 1985 to over 6 million hectares by 2007.Oil palm development contributes to deforestation - directly and indirectly. About half of all presently productive plantations (over 6 million hectares) were established in secondary forest and bush areas in Malaysia and Indonesia.
As palm oil is the cheapest vegetable oil, the demand for this commodity as a source of food and energy is expected to rise rapidly. The demand for food alone is expected to double in the next decade, and the Indonesian government has responded by setting a target to increase oil palm production from 20 million tonnes in 2009 to 40 million tonnes in 2020.If the Heart of Borneo were cleared for what would be unviable oil palm plantations, this would seriously affect the region’s water catchment role and would impact the region’s unique biodiversity. The unsuitability of the terrain may also result in large-scale soil erosion, flooding and increase the risk of fire.
There are other human uses which effect the characteristics of the rainforest at Borneo. Soil extraction is a huge investment for companies, who use high pressure hoses to drill in to the soil to extract nutrient load and nitrogen. This nutrient and nitrogen is useful for plant growth, therefore is used as a fertiliser. However, there are drawbacks to this as not only as rivers polluted by the chemical as it runs off in to rivers, but the characteristics of the rainforest is also damaged. The lack of nutrients in the soil makes it harder for plants to grow, as the plants on the litter layer rely on nutrients due to the lack of sunlight they receive.
Tourism has played a major role in to the characteristics of the rainforest at Borneo. Tourism has impacted both positively and negatively on the environment. Deforestation occurs in areas that are wanted for tourism. This removal of trees opens space on the ground floor which allows for buildings and tourist-related activities to be built. This interrupts the growth of plants and the succession is halted. Consequently, habitats are damaged, which puts many species in threat of becoming extinct. Among these endangered species in Borneo’s forest are: Sumatran Orangutan, Sumatran Tiger and the Yellow-crested Cockatoo.
Although the impact humans have on the biome mostly have negative effects on the characteristics present today, there are some which aim to maintain the forest. These are known as management strategies. The main ones are government incentives, conservation education and eco-tourism.
The Forest Stewardship Council are an eco-certified body, who work in the heart of Borneo. They work in synergy with The Sabah Forestry Department, to certify areas of Borneo’s forest to stop logging and clearing occurring. People have realised the negative effects of using the forest and exploiting it without compensating for it, therefore it has become evident to Borneo that the area needs to be preserved. It can be argued that it’s the conservation of the forest that has influenced the characteristics, such as high biodiversity and fragility.
Government incentives have been granted to try and manage the forest in a sustainable way. In 1996, the Government set aside a vast tract of remote rainforest to be protected. It was well respected at first and benefitted Sabahans as they got millions of dollars in scholarships. Borneo also launched a project known as ‘green print’, which aimed to conserve the forest. However, despite these positive incentives and attempts to protect the forest, from 1985-2001, 56% of the protected forest was cut down for logging.
In Sakau, Sabah, there is an eco-tourist rainforest lodge which aims to be sustainable in development. It is built on stilts, therefore does not disturb the litter layer beneath it. It is self-sufficient in water, and all rainfall is harvested. The building is ran on solar energy with hot water heating. The eco-tourism resort grows its own produce and sells them, benefitting its economy. It also employs local staff which are skilled to speak English, therefore they can educate tourists about the threats and sustainable opportunities the forest faces.
Although human management has attempted to manage the rainforest in Borneo sustainably, it can be argued that it isn’t actually the product of the present day characteristics. Its conservation has merely helped the rainforest to remain a clear, structured forest with layers. Yes, human management has enabled biodiversity to continue and to be established. But, it seems that human intervention has merely had a more negative impact on the biome. The characteristics of the forest being fragile, and broken up, with high rates of cleared areas, are a product of human interference. However, I would argue that climate has had a much more local effect on the rainforest and the flora and fauna within it. The characteristics of the biome are so unique and fragile, one of the most bio-diverse in the world. However, the complex issue of the forest is all down to the time and scale (temporal and spatial scale).
On a local scale, human interference seems to have a large effect on the characteristics present today, such as logging, mining, hydro-electric power stations, dams and tourism. However, on a global scale, climate dictates the biome. The equatorial biomes grow on the equator for a reason, where the temperature and weather is just right for them to grow. On a local scale, the climate of the rainforest is ever changing. It is thought that rainforests are becoming drier and the subject to droughts. This is thought to be due to the fact it is more and more effected as areas are being directly affected by humans. Not only are humans have a direct effect, but they are also having indirect effects all over the world, through global warming. This rise in temperature makes it harder for the ecosystem to develop. Similarly to this, the rising sea levels in the Maldives are a threat as corals can’t survive with sea levels above 25m. This rise in sea levels is due to the human influence on global warming.