Coral Reefs

Coral reefs

Source: Genetic Literacy Project

Source: From the Grapevine

There is no doubt: Coral reefs are some of the most stunning places on Earth and colourful and diverse ecosystems. Though the total area of the world's coral reefs amounts to less than one quarter of 1% of the entire marine environment, they have a huge effect on the health of the rest of the world (Mother Nature Network). Coral reefs are extremely important to life in the ocean. Healthy coral reefs mean healthy oceans which means healthy planet (Mother Nature Network). The variety of life supported by coral reefs rivals even that of the Amazonian or New Guinea tropical forests. Coral reefs are among the most biodiverse ecosystems on the planet (Darling and Fraser 2013) as they are home to tens of thousands of marine species. In fact, they are second only to rainforests in biodiversity of species. They cover less than 0.2% of our oceans but contain 25% of the world's marine fish species! Interestingly, although coral reefs are kind of like an enigma as they are among the most flourishing ecosystems on Earth, and they support high diversity and high biomass, yet they achieve this in some of the least fertile waters on Earth.

Defining Coral Reefs

Geologically speaking, reefs can be defined as “masses of carbonate limestone, built up from the sea floor by the accumulation of the skeletal material of many coral reef plants and animals”. They can also be described as “diverse underwater ecosystems held together by calcium carbonate structures secreted by corals”.  Corals are not plants - they're actually ancient animals and are relatives of jellyfish and anemones. They are built by “colonies of tiny animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups”. Corals are simple, clonal invertebrates that serve as ecosystem engineers, building living structures (reefs) so large that they can be seen from space (Burkepile and Hay 2008). It is important to note that a coral reef mustn’t be seen as a “biome” or “ecosystem”, but rather like a living community.

There are three types of reefs:

Source: Marinebio.net

·      Fringing reefs occur along shorelines of continents and islands. It is commonly found in Hawaii and the Caribbean. It gets its name from being closer to shore than a barrier reef. They are arranged like a fringe around the shallow waters.

Source: Wikipedia

 ·      Barrier reefs are found farther offshore and in deeper waters. They are found most often in the Indo-Pacific and Caribbean.

Source: Britannica

·         Atolls are a series of low coral islands surrounding a central lagoon, frequently found in the Indo-Pacific.

Source: Ducati Performance Parts

Each polyp excretes a calcium carbonate exoskeleton beneath it and, over an extended period, the skeletons of many coral colonies add up to build the structure of a coral reef.

Range and Location

Source: NOAA CoRIS

Coral reefs cover more than 250,000 km² of the ocean (all of them in the world add up to less than one per cent of the sea floor – an area about the size of France). Coral reefs are found all around the world in clear, tropical and subtropical oceans, and even in unexpected places have discovered cold water coral reefs off the coast of Norway and deep underwater in the Mediterranean Sea. The greatest diversity of species occurs in the Indo-Pacific region and a second, less diverse, region centred on the western Atlantic. One third of the world's coral reefs are located in South East Asia, hosting some of the highest levels of marine biodiversity on Earth. Coral reefs need water that is between 68 - 82°F (20 - 28°C), which is often located along the eastern shores of land. Corals live normally close to the surface where the sun's rays can reach the algae. They are typically found in shallow areas at a depth of less than 150 feet because they need sunlight to survive. But, some coral reefs can extend even deeper (up to about 450 feet deep).

Large coral reefs are rarely found in areas above 29 latitude where ocean temperatures fall below 18^oC for extended periods as this slows coral growth and their capacity to build large reefs (Burkepile and Hay 2008). Reefs are abundantly found in areas with shallow coastlines and clear, warm water where riverine discharge of sediments is low (Burkepile and Hay 2008). The most biologically diverse reefs occur in the tropical Indo-Pacific in the areas around Indonesia and the Philippines and house over 550 species of coral and thousands of species of fish (Burkepile and Hay 2008). The Great Barrier Reef off north-eastern Australia is the largest reef in the world with more than 2800 individual reefs occupying over 1800 km of the Australian coastline and can be seen from outer space (Burkepile and Hay 2008).

Diet

An individual coral (polyp) is a small organism consisting largely of a stomach topped by a tentacle-bearing mouth. These polyps extend their tentacles at night to sting and ingest tiny organisms (plankton) and other small creatures. Reefs only occur in shallow areas that are reachable by sunlight as a result of their relationship with algae. Many types of microscopic algae (Symbiodinium) live inside of the coral and provide them with food and help them to grow faster. In many ways, reef-building corals are animals that act like plants – they stay in one place and get some of their energy from the sun. Corals get most of their nutrients from the by-products of the algae's photosynthesis. But they also have barbed, venomous tentacles they stick out, usually at night, to grab zooplankton and even small fish.

Behaviour

They usually develop in areas that have a lot of wave action as the waves bring in food, nutrients and oxygen to the reef. Waves prevent sediment from falling on the reef. Reefs need calcium from the water to grow, which is often only available in shallow warm waters.

Importance of Coral Reefs

Coral reef ecosystems are important for many reasons:

·         Coral reefs are among the most biologically diverse and economically important ecosystems on the planet. Corals provide valuable and vital ecosystem services. They act as home and nursery grounds for many economically important marine species, protect coastlines from erosion, and provide food sources and income to millions of people living along coastlines (Zvulonic et al 2015). It provides immense ecological and economic benefits that contribute to the welfare of millions of people (Darling and Fraser 2013). They provide services that are vital to human societies and industries through fisheries, coastal protection, building materials, new biochemical compounds, and tourism.

·         They not only provide incredible value as wildlife habitat, but also protect coastlines from storms. Moreover they provide billions of dollars of food and jobs every year to people around the world.  

·         They form the nurseries for about a quarter of the ocean's fish - including commercially important species.

·         The biodiversity translates directly into food security, income, and a multitude of other benefits to people.

·      Coral reefs play an important role in the survival of our planet because it not only directly supports a marine ecosystem, but it also provides important benefits for mankind.

·         For several coastal areas, coral reefs are also able to provide an important barrier against storms, hurricanes, and typhoons.

·         Reefs assist also in being nurseries for large fish species, keeping them safe until they are large enough to strike out into the deeper ocean. A myriad of animals use coral reefs either as a stopping point (like an oasis) as they travel the deep blue sea, or they live as residents at the reef.

·         Coral reefs are vital for ocean and human health as well as our wellbeing.

·         Corals are tiny organisms (polyps) that attach themselves to the hard reef and live there indefinitely.

·         Coral reefs are valuable to the fishing and tourism industries, as well as protecting shorelines from storm damage.

·         Reefs are an important location for finding food, shelter, mates and places to reproduce.

·         They remove and recycle carbon dioxide (a gas that contributes to global warming).

·         They protect land from harsh weather by absorbing the impact from strong waves and storms.

·         They provide food, for example, lobster and conch. Coral reefs are also a huge tourist attraction.

·         Coral reefs are a large source of biodiversity.

·         Without the reef, many of these plants and animals would die.

·         Coral reefs are a useful educational tool as people can learn more about biomes and ecosystems, and the interrelationship between organisms and their environment by studying these coral reefs.

·         Particularly, fish, invertebrates, algae and microorganisms – make their homes on and around reefs.

·         A coral colony is formed when thousands of identical polyps live together.

Threats

Roughly one-quarter of coral reefs worldwide are already considered damaged beyond repair, with another two-thirds under serious threat (WWF). Scientists have predicted that in the next 50 years many of the coral reefs on Earth will be gone. We have already lost 27% of the world's coral reefs and if present rates of destruction continue, 60% of the world's coral reefs will be destroyed over the next 30 years. Reefs often recover from acute disturbances such as storms but infrequently recover from chronic disturbances. The coupling of acute natural disturbances with chronic anthropogenic disturbances often leads to precipitous declines in coral reef health (Burkepile and Hay 2008; Zvulonic et al 2015).

There are many problems facing not only coral reefs but also their habitats today. Coral reefs around the world have been declining at an alarming rate due to increasing human impacts. Despite the significance of coral reefs, these wildlife habitats are imperiled throughout the world. Sadly, fragile coral reefs that are already under increasing pressure associated with a range of natural and human causes has resulted in substantial degradation. This has ultimately led to a loss of coral cover and shifts in community structure. It should be noted that the impacts of these events have varied spatially and taxonomically. Even some of the most remote and pristine reefs are losing species. An estimated 75 per cent of remaining coral reefs are currently threatened. They are subject to many terrestrial, atmospheric, and oceanic influences. Many of these are directly related to human activities. Over the past years, losses and changes of marine biodiversity in coral reef ecosystems by anthropogenic activities, natural phenomena, and poor land management practices have become urgent issues (Zvulonic et al 2015). Coral reefs are also one of the most vulnerable ecosystems to climate change (these rapid environmental changes are occurring against a background of other widespread human-induced disturbances (anthropogenic activities) such as overexploitation, destructive fishing practices which removes species with important ecological functions, coastal runoff, coastal development, pollution,  climate change, ocean acidification, unsustainable tourism, and invasive species, which may ultimately stress corals to the brink of extinction (Darling and Fraser 2013; Zvulonic et al 2015; Burkepile and Hay 2008). Reefs located near human population centres are subjected to multiple stresses simultaneously and so suffer losses in diversity and cover. Meeting local demands can have multiple negative effects on the local environment. More than half of the world’s coral reefs are faced with high levels of human activities. The cumulative impacts of local and global stressors have resulted in widespread losses of live coral cover and an elevated risk of extinction to one-third of all reef-building corals.  The loss of healthy reefs may therefore limit the protection they can provide to coastal communities. The concept of resilience now underpins much of the thinking about the management of coral reefs (Darling and Fraser 2013).

Notably, coral reef ecosystems are particularly sensitive to climate-induced changes in the physical environment. Coral reef communities are likely to change in the future as reef organisms respond differently to various stressors. In order to predict future reef compositions, we apply estimates of coral and fish vulnerability to two key stressors; climate change (bleaching) and fishing. Most corals were vulnerable to one or both stressors, and future coral communities are likely to comprise stress-tolerant and weedy life histories (McClanahan et al 2014). Over the past 150 years, sea surface pH has dropped by 0.1 units and sea surface acidity has increased by 26% (Darling and Fraser 2013). Ocean warming and acidification are only two of the many manifestations of climate change. Other potential influences include sea level rise and changes in storm regimes caused by warmer SSTs (Darling and Fraser 2013).

Although biotic interactions (e.g., competition and herbivory) are emphasized as having important consequences for coral reef structure, abiotic disturbances such as hurricanes, temperature fluctuations, sedimentation stress, and sea-level change also produce long-lasting effects on reefs (Burkepile and Hay 2008).

Coral Bleaching

Coral bleaching is  rapidly becoming a global concern. Abnormally high ocean temperatures are being observed more frequently, and these temperatures could lead to mass bleaching event. Over the past century, average global sea surface temperatures (SSTs) have risen by 0.6 C and temperature anomalies, i.e., deviations from long-term temperature averages, are occurring more frequently (Darling and Fraser 2013). Furthermore, bleaching is caused by elevated sea surface temperatures, low temperature, sedimentation, extreme salinities or light levels, or bacterial infection.

 

Coral Bleaching - before and after. Source: New Heaven Dive School

Rising seawater temperature due to climatic changes is an extremely serious and global cause of stress to corals. When temperatures are too high, the relationship between corals and their symbiotic microalgae unfortunately breaks down. The algae are responsible for giving corals their mesmerizingly bright colour but when this occurs, corals appear white (“bleached”). Coral bleaching occurs when corals degrade or expel their dinoflagellate symbionts in response to environmental stressors such as elevated sea surface temperature and increased UV radiation. Just one degree above the typical summer max can cause corals to become bleached. What is more is that if the temperature is too high for too long, corals (and their microalgae) are unable to recover. Over the last couple of decades, bleaching has become more frequent, intense, and widespread which has ultimately led to massive, global die offs of corals (Burkepile and Hay 2008).

Source: Atlas Obscura

In severe cases, bleaching may occur on the scale of hundreds to thousands of kilometers and radically alter coral cover and composition with coral mortality from bleaching events approaching 100% in extreme cases (Burkepile and Hay 2008). Large-scale bleaching and mortality of branching corals can suppress fish populations that are dependent on live coral for shelter and food (Burkepile and Hay 2008). Moreover, due to warmer oceanic temperatures, there are more disease-related problems as these high-temperatures allow corals to become sick more easily, and allow disease-causing organisms to grow faster.

Ocean Acidification

Source: Sound Waves Monthly Newsletter - US Geological Survey

Ocean acidification is another serious threat to coral reefs. Because carbon dioxide (CO2) is more frequently released into the atmosphere and it has adverse effects on the oceans. Some of the excess CO2 from the atmosphere is absorbed by seawater which ultimately cases the oceans to become more acidic. Shockingly, the oceans’ acidity has increased by 25 per cent over the past 200 years. Consequently, these acidic conditions dissolve coral skeletons (which make up the structure of the reef) and limit coral to grow effectively. If something isn’t done, scientists estimate that the oceans could become 150 per cent more acidic by the end of this century. This will mean that corals will have a hard time to grow.

Fishing

Source: NOAA National Ocean Service

Coral reefs are negatively impacted by destructive fishing and exploitation to supply the coral reef wildlife trade. Frequently poisons (e.g. cyanide) are dumped into the water in order to stun fish to easily catch them. Sadly, it not only kills fish, but also corals, other forms of wildlife. This also leads to degrading the reef habitat. Overfishing affects the ecological balance of coral reef communities negatively, warping the food chain.

Sediments

Sediments, nutrients, and toxins released from deforestation, agriculture, and industry, are hydrologically transported to coral reefs through local rivers which ends up in the ocean, where it can 'smother' corals by depriving them of the light needed to survive.

Pollution

Source: NOAA National Ocean Service

Urban and industrial waste, sewage, agrochemicals, and oil pollution are unfortunately poisoning reefs as it is dumped directly into the ocean or carried by river systems from sources upstream. Sewage and runoff from farming increase nitrogen levels in seawater which causes an overgrowth of algae, ‘smothering’ reefs by cutting their sunlight off.

Climate change

Source: NOAA National Ocean Service

Climate change is an unprecedented threat. Corals cannot survive if the water temperature is too high. Unfortunately, global warming has already led to increased levels of coral bleaching and will increase in frequency and severity in the next few decades. Climate change is fundamentally altering ocean chemistry. Approximately one-third of atmospheric CO2 emissions are absorbed by the oceans and dissolve to reduce ocean pH, effectively increasing the acidity of seawater (Darling and Fraser 2013).  If even the conservative predictions of global climate models are realized, these climate changes could result in the fundamental reorganization of the ecology of coral reefs (Burkepile and Hay 2008).

Resilience

Resilience is a measure of the persistence of systems and of their ability to absorb change and disturbance, and still maintain the same relationships between populations or state variables. Ecosystems are dynamic, spatially and temporally heterogeneous, and can exist in multiple alternative states depending on environmental conditions. An ecosystem may be resilient for two reasons. On the one hand, an ecosystem may be resistant to a given perturbation. Carpenter et al. (2001) defined resistance as the amount of external pressure needed to bring about a given amount of disturbance in a system. On the other hand, two ecosystems may have similar resistance to a given perturbation, but may differ in their potential for recovery, that is their ability and/or swiftness to return to a state that is functionally similar to the pre-disturbance state (Darling and Fraser 2013).

Crazily cool facts about Coral Reefs

·         The Great Barrier Reef in Australia is the largest living thing on the planet.

Source: Science

Source: WWF

·      Reefs that are noticeable in size (like the aforementioned reef) are between 5 and 10,000 years old.

·         The Great Barrier Reef comprises of 900 smaller reefs! It covers about 1,200 miles (1900 km) and crosses over 500 islands. Unsurprisingly, it is one of the most visited reefs in the world, and, judging by the pictures below, one can easily see why:

Source: Serge the Concierge

·         The shape of a coral reef forms a natural protective barrier against storm waves and the waves break apart on the reef, so they don’t hit the shore at full force. A reef is called a “barrier” when its presence is able to protect the shallow waters along the shore from the open sea, thereby protecting and promoting the survival of several sea plants and animal life.

·         A coral reef is a community of life that lives and thrives in one location.

·         Interestingly, what we think of as the base of the reef and what we see when it is dry and removed from the water are only one small aspect of a living reef!

·         Various fish and sea creatures choose to spawn in reefs as their eggs will be safe from predators.

·         Coral reefs assist in improving the nearby water quality as they act as a filter, trapping things floating in the water, which makes for cleaner water all around.

·         Reefs essentially grow where there are stronger wave patterns and currents as it delivers more food for the ecosystem that creates the reef structure.

·         A coral reef needs sunlight to grow and, thus, they hardly ever grow in waters deeper than 45 feet.

·         Corals can be an assortment of colours, white, red, pink, green, blue, orange, and purple, due to natural pigments and the zooxanthellae in their tissues.

·         They also are more likely to be found in tropical oceans, as the water is clearer and warmer.

·         Coral reefs provide a space for feeding and raising babies for many of the sea mammals because the coral reef can stabilize the seabed for seagrasses.

·         Coral reefs play an imperative role in helping to manage carbon monoxide levels.

·         Wherever coral reefs grow, the sea bed is more stable and it helps seagrass and other sea plants to survive in the area. The more plants are growing on the sea bed, the less impact storms and surges will have on seabed too.

·         Coral reefs are found in 109 countries but significant reef degradation has occurred in 93 countries.

·         More than 80% of the world's shallow reefs are severely over-fished.

·         Southeast Asia is the global epicentre of marine diversity: Its 100,000km² of coral reefs (34% of the world's total) are home to over 600 of the 800 reef-building coral species in the world.

·         Indonesia and the Philippines hold 77% of Southeast Asia's coral reefs and nearly 80% of threatened reefs.

·         All corals have been listed under Appendix II of the Convention on International Trade of Endangered Species (CITES) since 1990.

·         More than 450 million people live within 60 kilometres of coral reefs, with the majority directly or indirectly deriving food and income from them.

·         There can be as many different types of fish in two acres of coral reef in Southeast Asia as there are species of birds on the entire continent of North America.

·         Corals are related to i.e. sea anemones and sea jellies. They make use of their tentacles for defence and to capture their prey.

Conclusion
Coral reefs have survived tens of thousands of years of natural change, but without urgent action to address threats, these beautiful and life-sustaining organisms could disappear, and their survival would be unknown.

References

Burt, J.A., Coles, S., van Lavieren, H., Taylor, O., Looker, E., & Samimi-Namin, K. 2015. Oman's coral reefs: A unique ecosystem challenged by natural and man-related stresses and in need of conservation. Marine Pollution Bulletin.

Burkepile, D.E. & Hay, M.E.2008. Coral Reefs. Elsevier B.V.

Chavanicha, S., Soong, K., Zvulonic, A., Rinkevichd, B., Alinoe, P.2015. Conservation, management, and restoration of coral reefs. Zoology 118 p. 132–134.

Darling, E.S. & Cote, I.M. 2013. Vulnerability of Coral Reefs.

McClanahan, T.R., Graham, N.A.J., & Darling, E.S. 2014. Current Opinion in Environmental Sustainability 7:59–64.

Websites

Mother Nature Network. Fascinating Facts about Coral Reefs. http://www.mnn.com/earth-matters/animals/blogs/5-fascinating-facts-about-coral-reefs

http://www.defenders.org/coral-reef/basic-facts

http://kids.nceas.ucsb.edu/biomes/coralreef.html

http://www.conserve-energy-future.com/top-25-coral-reef-facts.php

http://www.defenders.org/coral-reef/threats

http://wwf.panda.org/about_our_earth/blue_planet/coasts/coral_reefs/

http://www.conserve-energy-future.com/top-25-coral-reef-facts.php

http://www.mnn.com/earth-matters/animals/blogs/5-fascinating-facts-about-coral-reefs

http://wwf.panda.org/about_our_earth/blue_planet/coasts/coral_reefs/

http://wwf.panda.org/about_our_earth/blue_planet/coasts/coral_reefs/coral_facts/

http://kids.nceas.ucsb.edu/biomes/coralreef.html

Human-Environmental Interactions

Human-environment interaction is an overarching theme in Geography.  It can be described as interactions between human social systems and ecosystems. It concerns the numerous relationships (both positive and negative) between people and their surroundings. These systems are complex as they have many parts and are interconnected. Importantly, the type of society strongly influences people’s attitude towards nature, their behavior and, in turn, their impact on ecosystems.  Characteristics of human social systems comprise of population size, social organization, values, technology, wealth, education, and knowledge.

The relationship of man and environment is bi-directional, meaning that human beings are affected by the environment and they also affect the environment.

People modify the natural world for their purposes so that can obtain as much benefits from it as possible. Ecosystem services are essential human wellbeing, including the provision of resources like water, timber, food, energy, and land for farming.

Nevertheless, people’s actions have consequences on the environment. Undoubtedly, there exist a link between human activities and environmental degradation. The state of the environment has been significantly changed due to human activities. The activities have also exerted tremendous pressure on our natural world due to driving forces such as socio-economic and socio-cultural forces.

Furthermore, it relates to how people adapt behaviorally and physically to the environment and, conversely, how they depend on and modify it. In fact, people have caused such major environmental change that Nobel Prize-winning scientist Paul Crutzen suggested, in 2000, that we’ve entered an era known as the Anthropocene.

Depend - How do we rely on our environment to make our lives better?

We depend on the environment for food supply; energy source; air; water; natural resources for industry, and recreation

Modify - How do we change our environment to fit our needs?

Humans can impact our environment negatively, including: energy production; overuse of resources threatens natural balance; intensive agriculture leads to loss of diversity; and industry leads to pollution of air and water.

Adapt - How do we change ourselves to live within our environment?

The constituents of the study of interaction between environment and the human beings include:

1)      Physical Environment which is aspect of natural environment such as climate, terrain, temperature, rainfall, flora, fauna, etc.

2)      Social – Cultural Environment. It includes all aspects of cultural environment such as norms, customs, and process of socialization, etc.

3)      Environmental Orientations which refer to the beliefs that people hold about their environment.

4)      Environmental Behavior refers to the use of environment by people in the course of social interactions.

5)      Products of Behavior: These include the outcomes of people’s actions such as homes, cities, dams, schools, etc. Thus, these are products or outcomes dealing with the environment.

A relevant example of a human-environment interaction relates to climate change. Scientists wholeheartedly believe that there is evidence suggesting human activities have contributed to continuing changes in global temperatures and climates. Moreover, an attempt has been made by people to change these actions. In terms of adaption, speculatively, people will be forced to adapt to the effects of climate change in the coming decades.

Human-environment interactions entail how the natural environment shape, control, and constrain human systems by referring to natural hazards that disrupt human activity and how human decision-making and processes shape and, even change, the natural environment, including ecosystems, river systems, vegetation, and climate.

Sustainability

One thing is for sure, there is a greater concern about whether social and ecological systems can coexist in a sustainable manner. This has ultimately led to implementing the sustainability concept. It relates to whether and how human activities can exist without disrupting the ability of natural ecosystems to properly function.

The environment is a naturally-given capital, but it is exhaustible. Thus it is our duty to use resources sustainably and judiciously in order to properly conserve it for future generations.

Environmental concern

Nowadays there is a greater and growing concern about the deteriorating quality of environment. Fortunately, efforts have continually been made to improve the quality and to ensure the sustainable use of resources. The effect of human activities is long-term and irreversible and will affect the lives of generations to come.

We don’t always realize that even our simple activities play an inevitably role in degrading the environment. All billions of people living on our planet affect the environment in some form or another. The majority of people, through their unsustainable activities, have a collective, negative effect on the environment in which we live. An appropriate example is air pollution.

Water, a natural resource, is a finite resource that isn’t being replenished fast enough.

We must help to sustain our planet for not only our own lives but also for future generations to come. The only way that this will take effectively place, is if theirs is equilibrium between the humans and their activities and the environment.

References

Man-Environment Interaction – Module V. Social and Applied Psychology.

Websites

http://www.uni-kiel.de/ecology/users/fmueller/salzau2006/studentpages/Human_Environmental_Interactions/index.html

https://www.reference.com/science/human-environment-interaction-8783e2b596fcb835#

https://www.e-education.psu.edu/geog030/node/319

Deforestation and Desertification: A comprehensive look at its causes, contributors, spatial and temporal characteristic and human impacts thereof

Two of the most important and widespread environmental changes will be discussed in detail. The first is the occurrence of deforestation which is globally a problem and desertification also occurring on the majority of continents. Deforestation has an impact on desertification. Various aspects such as the spatial and temporal scale, the causes, and contributors of such manifestation, as well as human impacts and whether all types of global environmental change can be generalised, will be comprehensively considered.

Introduction to Deforestation
An important environmental issue, deforestation, is both a complex global and local problem and Africa, being a developing continent, is being most widely and devastatingly affected by such rapid occurrence. It compromises the notion of sustainable development by impacting the environment in a very immediate and detrimental way. Even though forests play an imperatively environmental vital role, as it supports vital ecosystems and houses a myriad of fauna and flora, it is being destroyed and cleared at an astronomically fast rate without having enough time to restore itself, causing inestimable habitat changes, as well as reducing carbon storage. The United Nations Food and Agriculture Organization (FAO) estimated that, from 1990 to 1995, the annual loss was estimated at 12.7 million hectares Furthermore, deforestation account for roughly one-sixth of total anthropogenic emissions of greenhouse gases and degradation may account for 10% of total emissions in the tropics. Tropical deforestation is responsible for 6–17% of global carbon dioxide emissions that affect climate change (Angelsen & Kaimowitz 1999; Pfaff et. al 2013; Cassea et. al 2004).

Spatial characteristics
It is widely known that deforestation occurs in both developed and developing countries, but at different geographical contexts in specific localities and are characterised by different regional aspects, such as aridity, as well as diverse human-environment conditions. For example, deforestation occurring in Africa will markedly differ from that occurring in Asia because of factors such as poverty and a more arid climate. Each type experiences deforestation at a different rate and extent. Within Brazil, as in most tropical countries, the native forests are being lost through conversion to agriculture”. Brazil and Indonesia have accounted for a large portion of the global deforestation totals. The scale (magnitude) at which it occurs also significantly differs as it can either be on a small or larger scale, depending on what kind of activities (e.g. agricultural and logging) take place. Tropical forests are disappearing as a result of many pressures, both local and regional, acting in various combinations in different geographical locations. Some of the most important places where deforestation is taking place, specifically in developing countries, include Africa, in particular the Congo, in South America, referring to Peru and Brazil, and India, Indonesia, and China as well as developed countries, such as Russia, Canada, the USA, and Australia (Pfaff et. al 2013; Geist and Lambin 2002).

   Map 1: Deforestation data on occurrence around the world (Source: The World Bank 2011).

Deforestation, concisely described as the permanent clearing of forests, takes place as a result of myriad activities, most notably include agricultural expansion, such as permanent and shifting cultivation, cattle ranching, and wood extraction for commercial use as well as fuelwood and charcoal production.

Causes and contributors of deforestation
Deforestation occurs at different times at different regions around the world as land use changes, leading to deforestation, varies over time. Forests are depleted over a few years and are used for different activities. As a result of multifaceted socio-economic and geographical problems, especially faced by Africa, deforestation is taking place. Mostly notably the highest contributors to deforestation are small farmers, forest-dependent people, loggers, ranchers, as well as plantation companies.

There are several explanation as why forests are shrinking significantly. However, Cassea et. al (2004) argue that “it is more difficult to establish links between underlying factors and deforestation than between direct or immediate causes and deforestation”. Nonetheless, a clear distinction can be made between direct, proximate causes that directly impact forest cover, that originate from intended land use, pertaining from agriculture activities and expansion, wood collection, infrastructure extension, pasture land as well as indirect, underlying causes underpinning the direct causes which include social processes, referring to migration, human population dynamics, export prices, property rights, and government policies. This clearly indicates that socio-economic considerations impact deforestation considerably. Deforestation is driven by identifiable regional patterns of causal factor synergies, referring to economic factors, institutions, national policies, and remote influences driving agricultural expansion, wood extraction, and infrastructure extension (Cassea et. al 2004; Geist and Lambin 2002; Pfaff et. al 2013; Angelsen & Kaimowitz 1999).

There is one primary and direct factor which contributes the most to deforestation and land-use changes, namely, agricultural expansion. It includes forest conversion for permanent cropping, cattle ranching, shifting cultivation, and colonization agriculture. In permanent cultivation, the expansion of food-crop cultivation for subsistence is three times more frequently reported than the expansion of commercial farming (less than 25% for all regions). This is particular true for developing countries. Land is frequently converted to pasture or crops when forest is cleared. At the underlying, indirect level, deforestation can be attributed to driving factors that act synergistically and being driven by the interplay of economic, institutional, technological, cultural, and demographic variables.

Economic rationality
It is no surprise that economic factors, too, lead to deforestation as commercialization and the growth of timber markets and market failures drive deforestation. Such economic variables can include low domestic costs (for land, labour, fuel, or timber), product price increases (mostly for cash crops) and the requirement to generate foreign exchange earnings also has an impact. By clearing forests it is possible to create agricultural land, higher prices for agricultural products, produce staple food, commodities (e.g. biofuel), and even profiting from timber sales. Thus, there are socio-economic incentive to exploit forests in this way. As frontier agriculture becomes more profitable, both the existing population and migrants from other areas begin to shift resources into forest clearing. Development also impact the rate at which deforestation occur. Ecosystem services don’t generate revenue, thus aren’t part of many countries’ decision-making processes (Angelsen & Kaimowitz 1999; Geist and Lambin 2002).

Institutional factors
These relates to formal pro-deforestation measure including land use policies and economic development of colonisation, transportation (for agriculture and logging and fuelwood collection), and policy failures (e.g. corruption).

Technological factors
These include agro-technological change, with agricultural intensification having no distinct impact separate from agricultural expansion, and poor technological applications in the wood sector (leading to wasteful logging practices). Technology has both a direct effect on farmers’ behaviour and an indirect effect resulting from its impact on product and factor prices (including wages)(Geist and Lambin 2002; Angelsen & Kaimowitz 1999).

Cultural or socio-political factors
These include variables such as economic and policy forces and attitudes of the public.

Demographic factors
In-migration and population pressures also lead contribute to it. An increase in population density is also stressful on forests as this land is used for construction, fuel, and agriculture.

Other discernible causes can also be included, such as land use and clearing for housing and as a result of urbanisation, wildfires and overgrazing can unintentionally lead to the clearing of forests, fire charcoal and palm oil production (especially in Indonesia and Malaysia and in some parts of Africa), and mining are also a contributor, farmers clear forests to plant and cultivate staple crops or to let livestock graze on land. When land productivity declines, the land is furthered exploited for cattle grazing. People, especially poor people, who live close to forests are dependent on it to sustain themselves, as their subsistence depends on the source of forests as it provides critical fuelwood and food sources. Therefore, their livelihoods depends on an unlimited forest resource.

Human influences on phenomena
It is indisputable and inevitable that anthropogenic activities can, and have, caused deforestation to take place at an accelerated rate. In fact, humans are the primary cause of such clearing of forests. Many people, especially in the poorer, more developing parts of the world, forests are a source for survival and subsistence and rely totally on it and therefore are forest-dependent people. Farmers, loggers and ranchers modify the land to suit their needs, and forging and collecting wood from the land, thereby altering the quality of the forest.

Introduction to Desertification
Desertification is principally a man-made phenomenon and a widespread and irretrievable type of land degradation which occurs primarily in dryland environments. Desertification is linked to global environmental change through climate, biodiversity loss, human dimensions, and land change”. Over the last couple of years, desertification has rapidly occurred which has led to the considerable loss of arable land, leading to marginalisation. Desertification is the spread of desert-like conditions in arid and semi-arid conditions. It is a result of pressure from both climatic and human factors (Laki 1994; Middleton 2008; Phillips 1993). Phillips (1993) further elaborates, stating that “it may be the result of inherent biophysical feedbacks in dryland systems”. The UN Convention to Combat Desertification (as cited in Middleton 2008) defines desertification as “land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic variations and human activities. At least 35% of the earth’s land surface is threatened, inhabited by 20 % of the world’s population.” Many earth surface systems are unstable, and thus such aspects would inevitably lead to permanent decline. Natural vegetation clearing has taken place at a considerably fast rate, especially over the last couple of years which leads to desertification.

Spatial characteristics
Desertification specifically occurs in drylands, including arid, semi-arid, and dry subhumid zones. For example, in the Sahel, high pressure air-mass movement is thought to have contributed to desertification (Laki 1994). Food security inexorably affect desertification. Phillips (1993) notes that “this degradation occurs on all continents (except Antarctica)” indicating just how extensive and its reach truly are and that it takes place in spite of geology and temperature variances.

Map 2: Global Desertification Vulnerability - Source: United States Department of Agriculture 2003.

Causes and contributors of desertification
Land that are extensively used, contribute to desertification and as Middleton (2008) note, “they can be classified in intensive grazing, wood cutting, livestock overpopulation, over cultivation, overexploitation of vegetation, and a high demand for water resources”. These worries then lead to an inherent instability in vulnerable areas. These all have an exponential and long-term impact on the environment. Salinization of irrigated cropland is also responsible. Laki (1994) notes that the main factors contributing to desertification include “drought, population growth, the spread of extensive agriculture, deforestation, rapid urbanization, the erosion of local political power, the lack of economic institutions and the absence of social institutions which have tended to reduce the capacity of the local people to cope with the resource degradation problem”. Thus, like in the case of deforestation, it is widely influenced by human-induced activities, but also because of climatic factors such as climate change. It also, in turn, causes weather fluctuations especially drought. This have an enormous detrimental impact on valuable ecosystems. As such, desertification is a serious ecological problem and as Laki (1994) argues “the rate at which the process has been occurring has been estimated at 5-10 km per year”. Furthermore, erosion will take place as there is no vegetation cover. Land-ownership patterns also lead to desertification.

An enormous human population growth has occurred in the areas that are facing desertification, coupled with the inevitable need for natural resources, but the land can’t sustain all of these demands. Drought, naturally occurring or exacerbated by the human stresses and exploitation of land resources, have also resulted in greater occurrences of desertification. Different physical factors of soil are influenced by desertification, including depth, organic matter and the fertility of soil.

Desertification can thus be divided in three broad causes: continuing climatic changes; short-term weather oscillations; and human factors. In these regions, the ecological balance between climatic conditions, soil, vegetation cover, animal life and soil biota is so precarious that any incidental vicissitude may upset it’. The damage may be irreversible with severe and continued misuse (Laki 1994). Phillips (1993) argues that “the two-way relationships between seven key components in desertification (vegetation, albedo, temperature, precipitation, soil moisture, wind erosion, and water erosion) result in inherent instability”.

Arid areas are exceedingly influenced by climate. The climate of these arid lands is characterized by highly variable rainfall, high temperatures, strong winds and high evapotranspiration rates that exceed annual average (Laki 1994). Desertification leads to significant changes in microclimates. A reduction in rainfall, also unavoidably causes desertification. Soil worsening can be ascribe to human settlements but also their animals. Sand encroachment also lead to a decline in vegetation. Resource abuse (over cultivation, overgrazing, and woodcutting) is primarily responsible for desertification. Agricultural activities are exposing the soils to water and wind erosion.

As Laki (1994) explains, “marginal areas are brought into cultivation during periods of high rainfall. When dry years follow wet, the ploughed loose soil is susceptible to wind erosion, where the clays and silts are carried away as dust and the sand drifts to form dunes”. Deforestation contributes to desertification by making the microclimate more arid. Burning of grasslands is also a major contributor to desertification. Laki (1994) notes that “fire destroys forage and induces changes in the botanical composition of the predominant vegetation formations and communities”. The impact of desertification is also widespread which include hunger and thirst, as crop and animal production deteriorates. Which in turn leads to poverty and a loss of home, and can lead to a loss of life too.

Human influences on phenomena
Even though desertification can be triggered by climate variability (e.g. drought), it is irrefutable that form the above-mentioned statistics and data, desertification inevitably and inextricably are influenced by anthropogenic activities. Numerous examples such as overgrazing, intensive grazing, wood cutting, overpopulation, over cultivation, overexploitation of vegetation, and a high demand for water resources all occur as result of medication or altering the land for human’s needs. One thing is sure, desertification is highly unpredictable and is certainly exacerbated by human-induced land activities.

Conclusion
For deforestation it would be wrong to assume that it will and have the same causes and contributors. Many parts are primarily concerned with technological and economic advancement (thus capital-driven) and in other parts, like Africa who is a developing world, many people solely rely on forests for their fuelwood and food. Thus different causes will result from this. Different localities experience different causes, for example, in Africa it is more arid and poverty will also occur more frequently. The rate and extent of the occurrence of deforestation will also vary tremendously among differ parts of the world.

Both deforestation and desertification are two of the most important (and detrimental) environmental changes facing the world today. The poorer communities which live close to forests and deserts are the most vulnerable to such changes. It is clear that desertification can both be influenced by biophysical and socio-economic factors. It is intensified and exacerbated by human-induced land activities that are taking at an unsustainably rate place.

References
Angelsen, A., & Kaimowitz, D. 1999. The International Bank for Reconstruction and Development: Rethinking the Causes of Deforestation: Lessons from Economic Models. The World Bank Research Observer vol. 14, no. 1. pp. 73–98.

Cassea, T., Milhøjb, A., Ranaivosonc, S., Randriamanarivoc, J.R. 2004. Causes of deforestation in southwestern Madagascar: what do we know? Forest Policy and Economics 6 (2004) 33–48.

Geist, H.J., &  Lambin, E.F. 2002. Proximate Causes and Underlying Driving Forces of Tropical Deforestation. BioScience Journal Vol. 52 No. 2 p. 143-150.

The World Bank. 2011. Data and Statistics: Deforestation.

Laki, S.L. 1994. Desertification in the Sudan: causes, effects and policy options. International Journal of Sustainable Development & World Ecology, 1:3, 198-205.

Middleton, N. 2008. The Global Casino: An introduction to Environmental Issues. 4th Edition. Hodder Education: London.

Pfaff, A., Amacher, GS., Sills., EO., Coren, MJ., Streck, C., & Lawlor, K. 2013. Deforestation and Forest Degradation: Concerns, Causes, Policies, and Their Impacts. Encyclopedia of Energy, Natural Resource and Environmental Economics.

Phillips, J.D. 1993. Biophysical Feedbacks and the Risks of Desertification, Annals of the Association of American Geographers, 83:4, 630-640.

Reynolds, J.F., D. Mark Stafford-Smith, D.M., & Lambin, E. 2003. Do Humans Cause Deserts? An Old Problem Through The Lens Of A New Framework: The Dahlem. Proceedings of the VIIth International Rangelands Congress August 2003, Durban.

United States Department of Agriculture. 2003. Natural Resources Conservation Service: Soils- Global Desertification Vulnerability.