Biodiversity – the complete story
The year 2010 has been declared as the International Year of Biodiversity. Biodiversity is a relatively new field of study in the scientific world, but in recent years the term has been used extensively, among scientists, environmentalists, politicians and in the media yet the definition of Biodiversity is often difficult to fully communicate because of the vast scope of components it encompasses.
There are various definitions of biodiversity; many definitions although correct in a sense, lack some vital element which is a key component of biodiversity. Essentially, Biodiversity is the variety of life within a given area, ecosystem or biome. It includes all the species present in an area, the genetics within each species, the relationships between species as well as elements of the landscape within that community. Noss (1990) recognised three main attributes of biodiversity; composition, structure and function.Composition shows the identity and species richness of the biotic components as well as the relative amount (i.e. abundance, cover and biomass). The biotic components of biodiversity are the genes, organisms, family units, population, species and other taxonomic classifications. Structural attributes refer to the elements of a community or landscape: the shape, space arrangement and size of the vegetation community, as well as the density of foliage cover and height, as well as relative ages and trophic structures. Bioticfunctions include processes: herbivory, predation, parasitism, mortality, production, vegetative succession, nutrient and energy cycling, colonization, extinction, genetic drift and mutations. The complexity of biodiversity is more than the sum of its parts. Each element mentioned above will contribute to the biodiversity of a region but more importantly the interactions between them and their effect on each other will impact directly or indirectly on the biodiversity of a region.
With such a complex configuration, encompassing multiple factors and so many variables, it is no wonder that a neat definition for biodiversity is still lacking. When we talk about biodiversity it encompasses all of these aspects, but to simplify matters let’s define Biodiversity as the variation of life, all forms of life in the plant and animal kingdom, down to the microscopic elements such as single-celled organisms, as well as the relationships and processes between these life forms. In short, Biodiversity is dynamic, always changing. Therefore, the more we learn and the better we understand the factors and processes contributing to the sustainability of biodiversity the more success we may have in effectively conserving it.
There have been various estimates of the number of species currently living on Earth, the range has been extensive; largely because most species are micro organisms and tiny invertebrates. Most estimates fall between 5 million and 30 million species currently living on our planet, roughly 1.75 million species have been formally described and officially named and more than half of these are insects. Up until recently the study efforts were concentrated on the macroscopic, i.e.: that which we can see with the naked eye. Additionally because regions of high biodiversity correlate with the tropic regions, countries in these areas tend to be the under-developed world and lack the resources and expertise to taxonomically identify and classify species.
Following that there are so many factors which impact on biodiversity it is no surprise that biodiversity is not evenly distributed across the globe. In fact there are several distinct patterns in biodiversity which have intrigued ecologists for years. The most obvious pattern is the latitudinal gradient, which shows that species diversity increases as latitude decreases, i.e. there are noticeably more species found in the tropics than in the temperate regions, and even fewer as you approach the Polar Regions. Although this pattern has been extensively researched in the terrestrial ecosystems whether is exists in aquatic ecosystems is yet to be determined, largely due to a lack of study in these areas. Some of the reasons attributed to the higher diversity in the tropics are; increased surface area, which allows more species to co-exist at population densities which make them less vulnerable to extinction. Other factors include; soil types, rainfall patterns, energy availability in terms of sunlight which is essential to the growth of plants, which form the base of the food chain.
In nature there are several factors which influence the biodiversity in a community; disturbance events such as fires determine the type of species which can inhabit an area. Habitats such as the Cape Floristic Region in Southern Africa are dependent on fires for the dispersal of their seeds. Fires clear the undergrowth of other species and leave it open for new seeds to germinate and establish themselves without competition from other species.
Competition between species for resources is a major factor affecting community structures and hence biodiversity. Strong competitors will exclude others from an area and thereby reducing the diversity of an area. As conditions change some species may thrive and become stronger competitors through adaptation to their environment. Predation will exert top down control in a community as predator species regulate the number of prey species, and may favour one species over another. This will effectively decrease the population of the preferred species giving other non prey species an advantage. Prey species will also exert a bottom up control on predator numbers through being a limited resource, the population of predator species will be proportional to the amount of prey available. E.g.: the number of lions in a game reserve will depend on the game available for them to eat. If the lions prefer Zebra to wildebeest and eat more of these the wildebeest population will expand and the zebra population will be kept down by the lions but if the all the zebra are eaten, the lions will have to switch to another type of prey. A pride of 20 lions will require more meat than a pride of 10 so if the prey numbers decrease and food is scarce for the lions, eventually the number of lions will decrease. The dynamics of a community mean that interspecies relations will influence all species within the community either directly or indirectly!
We have seen that species interactions have an influence on the biodiversity of a community through a variety of ways. These become a key factor with the introduction of exotic species to an area. Exotic species can be defined as those species which are not naturally found within a specific area or country. Exotic species are introduced into an area either wilfully or unintentionally through human activity. E.g. ships moving between continents often carry rodents, insects and plant seeds on board which are then transferred when the ship docks at its next port. With the expansion of the global village and the increase in international travel the process has been accelerated even further. Examples of intentional introductions occur when commercially important crops are introduced to a country for agriculture, or when insects are introduced for a specific function e.g.: pollinators. To a certain extent, the immigration of new species into an area is a natural process, and has been occurring over time as environmental conditions change and allow species to expand their ranges into previously unsuitable areas. As species move, they in turn alter the local environmental conditions which will have a knock on effect for other species in the area. Often the effects an exotic species will have on a system are unknown until it is too late and the damage has already started. Species interactions are affected and the system ultimately changes, unable to remain functional under the pressure exerted by a new species.
Ecosystems are so complex and interlinked that it is difficult to determine a starting point for the classification of indigenous species. You may ask: “Where do we draw the line in history and say that from that point all species in an area and indigenous and any new species will be classified as exotic?” Scientists have classified 7 biomes of terrestrial systems, and within each biome there are ecosystems and vegetation types in which there are specific indicator species. Therefore species which are not included in the description for a specific area or fall into another classification can be treated as exotic. Some exotic species have little or no detrimental effect on their new environment, but too often exotic species can be devastating when introduced into a new environment and there are many well documented studies on such events. Various ecosystems around the world are under sever threat due to the invasion of alien species, and environmentalists and land owners are working persistently to remove these from the environment, but it is a constant battle.
Initially the introduction of a new species will increase diversity of an area but exotic species are often aggressive species with evolutionary traits which make them highly adaptable or strong competitors and therefore they soon out compete local species for resources enabling them to become well established and spread quickly, effectively reducing the population or totally excluding the growth of indigenous species eventually reducing the biodiversity of an area. In addition, exotic species often have no natural predators in the area therefore their population growth becomes exponential and can destroy the habitat for a multitude of other species, causing entire system s to collapse.
For the last 10,000 years the activities of man has been the greatest factor affecting biodiversity, with adverse impacts occurring at an accelerated pace since the onset of the industrial revolution. The development and expansion of the human population has lead to interference in ecosystem functioning through habitat destruction and fragmentation, over exploitation and pollution including air, water and soil pollution. Habitat destruction has been identified as a major contributing factor to the loss of biodiversity globally. Even if no further loss was to occur vulnerable species would still face extinction as a result of the extensive existing damage. We face an ever growing list of endangered species which many well meaning groups are focused on protecting, but conservation requires more than the preservation of a species, it requires the protection of their habitat as well, which comprises of an abundance of species, all of which contribute to the survival of each other. The same is true for humans, our survival depends on the survival of others.
As the global human population expands so does the need for food and other materials, leading to more natural land being converted from wilderness to agricultural, mining, lumbering and urban areas. Agriculture sees the plantation of a few commercially important crops being farmed over extensive areas which used to host a multitude of species. Having one species, often from a small genetic base leaves the crop susceptible to destruction through a single pathogen, when we lose genetic biodiversity and wild species, we loss the potential beneficial traits that they may have had. Whilst we selectively bread for a favourable trait, e.g. higher yield we may also breed a variety that is susceptible to disease. We then plant hundreds of acres with this one species in order to maximise the return on yield and yet a single disease could potentially destroy the entire crop. Our insatiable need for more, fuels the destruction of habitats which are home to thousands of species many of which have now gone extinct or are precariously perched on the edge of survival. The consequences of these losses are still not entirely understood but the looming threat to ecosystem functioning is a threat to the survival of our own species.
Apart from the loss of potential resources we lose the services already provided by the ecosystem, since time began the natural world has been evolving, changing and adapting. It’s not by change that mangroves occur along the edge of terrestrial and aquatic environments; their presence has a function and makes that environment more stable and more productive. Tropical forests hold vast stores of fresh water and prevent flooding, soil erosion and the loss of nutrients from the land. Even the frozen glaciers of the Polar Regions are connected in the cyclic nature of earth. When one species starts to remove these for its own benefit the benefit is short lived but the consequences are far reaching for all species. Nature has the remarkable ability to restore herself if allowed to do so, the question is: “will we humans allow her to? For our own sake, can we afford not to?”
In biodiversity there is a great amount of redundancy which is essential for the sustainability of ecosystem functioning. Ideally there are several species whose functions within the ecosystem overlap, thereby maintaining a fully functional system. To use an analogy let’s say you have a top class Law firm operating in a city. This firm has several secretaries, including a receptionist , who work for the partners and their functions overlap to some extent, they each represent a species in the system. Now let’s say the receptionist goes on maternity leave, representing a local species extinction, instead of replacing her the firm decides that each of the secretaries will have an hour shift at the front desk, this increases their work load but they can still cope and the firm continues functioning as before. But then one of the secretaries falls ill and is off work for several days, now the pressure is mounting on the remaining secretaries as there is still the same amount of work to complete but there are now fewer of them doing it. And then the firm lands a huge client with a very important case so the work load is suddenly doubled. In nature this would equate to a sudden dump of excess nutrients on the system which needs to be regulated. In the law firm the secretaries would not cope, work would pile up and things would go undone, the productivity of the office would decline and the entire system would start to feel the effects. Similarly in the ecosystem, the break down in one link would put strain on the remaining structure causing it to eventually collapse. If the system can be restored before this happens, i.e. the secretary on sick leave returns and can continue her work the system will again achieve balance and continue to function. This is why redundancy, i.e. the excess of species in a system providing a similar function is essential to maintaining the system. BIODIVERSITY provides this redundancy!
The processes which are linked to biodiversity in a region are of great benefit to humans, although many of these services are not readily observable and therefore have largely gone unnoticed in the past. However, as ecosystems are disrupted often the function provided by the system is suddenly noticed when problems arise. For example; wetlands act as giant sponges, absorbing excess water, either from rainfall or surging rivers, preventing potential flooding downstream and then slowly releasing the water over time. They are also highly efficient natural water treatment works, absorbing chemicals, filtering pollutants and sediments, breaking down suspended solids, and neutralising harmful bacteria. Thereby cleaning the water before it is released back into the environment and efficiently using the organic content. Without wetlands, large volumes of heavily sedimented water rush downstream, harming fragile ecosystems downstream. This sediment is eventually dumped in estuaries or the shallow coastal regions. Both of these are themselves essential ecosystem. Estuaries play a role in the life cycle of many marine and fresh water species, and are used as nurseries because they provide a safe, nutrient rich environment for juvenile organisms. But since 1900, more than 50% of the world’s wetlands have disappeared – largely due to human activities. Because natural systems are so closely linked with each other, the loss of one will degrade and potentially threaten the functioning of the other.
Ecosystem functioning is essentially the driving force behind the natural world. Living organisms play central roles in the systems which cycle major elements such as carbon, nitrogen, water and oxygen. Insect pollination, water and air purification, nutrient cycling are all provided free of charge through natural systems which experiments have shown would be extremely complex for humans to recreate. Surely it is cheaper to conserve and maintain what we already have, rather than trying to do it ourselves? Or we could ask, “what would the world be like without these services?”
Ecosystems provide us with our most basic needs; water, food, energy, shelter, medicines. Although 80% of human food supply comes from just 20 kinds of plants, humans use up to 40,000 species each day and considering the volume of species we have on earth there remains an untapped potential for more species to be utilised. Additionally, the food we consume is in some way dependent on other species, which we do not directly consume. Plants are heavily dependent on microorganisms in the soil which are essential to nutrient cycling. Livestock, which are a protein source for human also need to eat; therefore the species which provide them with food indirectly feed humans.
The ocean is home to a host of species many of which are a primary food source for coastal dwellers. In fact, fish stocks are a protein source for over a billion people worldwide, and are also used as a protein supplement for other livestock, such as poultry. Seafood products are one of the most widely traded commodities, worth billions of dollars annually and contribute substantially to some countries economies. But fish stocks are continually under threat from over fishing and the ocean is a sort of “no man’s land”. It exists beyond countries boarders and though we are all benefiting from its service it is more difficult to protect due to the sheer vastness of the ocean and the fact that you can’t establish boundaries like fences in the ocean to conserve areas. This is somewhat overcome with the establishment of Marine Protected Areas (MPAs). Areas which are important in the life cycle of commercial fish stock species, including their spawning grounds and nurseries, are identified and actively protected by the country off whose coastal area they are located. Thus providing a safe haven for young fish to grow, mature and reproduce before they are caught, thereby ensuring the next generation of the species. Allowing fish to grow to larger sizes within these MPAs has added benefits as larger fish produce more eggs. In addition to fish stocks, oceans play a pivotal role in the earth’s climate and regulating the oxygen in the atmosphere, oxygen is what we breathe, without it the human body won’t last more than 3 minutes.
Mangrove swamps and coral reefs provide protection to coastal zones from hurricanes, storms, cyclones and rough seas. In 2004, a Tsunami devastated parts of the South and Southeast Asia. The communities with healthy coastal habitats, including mangroves, coastal vegetation and coral reefs, were less severely impacted than those with damaged habitats.
In an effort to demonstrate the importance of ecosystem functioning the ICUN calculated the monetary value of the goods and services provided by ecosystems, the estimated amount was US$33, 000,000,000,000 (US$33 trillion) annually. That’s more than double the United States GDP for 2008!!! For the sake of our own survival we cannot afford to lose ecosystems as we rely on them so heavily. Since biodiversity is often used as a measure of healthy ecosystem one can conclude that the loss of biodiversity would essentially jeopardize ecosystem function and thereby threaten our own survival! Our current lifestyles are far from sustainable. We use 40% more resources that natural systems can restore in a year, in fact we need 1.4 planets to sustain our lifestyles, we only have ONE EARTH. Yet we continue to cut trees, faster than they can grow, catch fish before than can reproduce, use water irresponsible and at the same time remove the natural systems that regenerate fresh water. Fresh water habitats are currently the MOST threatened ecosystems, yet it is the most precious resource for life. Pollution of these environments through siltation, chemicals, fertilizers, sewage all of which have a devastating effect on the organisms in these environments, directly impacts the supply of fresh water to human populations. In your own home try to live one day without fresh water… you will soon realise how dependent you are on it and maybe realise how much we waste and hopefully change your habits to conserve water! Can you really afford to wait for others to save water when it is so important for your own existence?
Currently, the number of species faced with extinction far outstrips the available conservation resources. Therefore across the globe certain “hotspots” of biodiversity were identified in order to focus conservation efforts where exceptional concentrations of endemic species are found in a region which has experienced extensive habitat loss. The aim of identifying hotspots is to focus conservation efforts into identified areas and by protecting the plant diversity of the region the associated fauna will be protected. The two criteria for a region to be identified as a hotspot are (1) it must have 1500 plant species as endemics and (2) it must have lost 70% of its original habitat. In the initial study 25 regions were identified as biodiversity hotspots which collectively contained 44% of all plant species and 35% of vertebrate species, the combined area comprised only 1.4% of the total surface of the earth.
There have been many criticisms of hotpots which some people believe are selected due to their aesthetic value which encourages funding and public support for their conservation whilst other areas with higher endemism but have less aesthetic value are left unprotected. 16 of these hotpots were located in the tropics and most of them are forests, this creates a problem as forest dwelling species will be protected whilst other biomes will go unprotected and the species associated with them will be at risk.
For instance the grasslands of southern Africa are unique ecosystems with a rich and often highly specialized animal life, both above and below ground. In fact, the Grassland Biome has an extremely high biodiversity, second only to the Fynbos Biome. The features which make grasslands unique have also made them ideal for agriculture and therefore they are under serious threat. Species-rich montane grasslands are currently being destroyed at an average rate of over 200 km2 per annum by commercial afforestation alone, what’s even worse is that transformation of grassland by ploughing and afforestation is considered irreversible. Additionally, urbanization is a major influence on the loss of natural grasslands. This biome is not only one of the most poorly conserved, but there is little potential for conservation in the future because of its radically altered state. In fact, it is doubtful whether certain representative veld types within the Grassland Biome can ever be adequately conserved today, simply because there are no reasonably big areas remaining. If conservation efforts are to have a real impact on conserving biodiversity it is essential that emphasis is placed on biologically important regions regardless of the social or political situation and we do whatever is necessary to overcome such obstacles.
Across continents, policy, attitudes and general ability towards conservation are as varied as the landscape. This can be attributed to the fact that ecosystem services and resources are considered public goods, being the property of no man but the country at large. Decisions made at political level are driven by economics and bottom lines and they have overlooked the long term effects. They also overlook public benefits in favour of private benefits and focus on short term profitability rather than the sustained supply of resources over an extended time frame. Too often the decision makers are insensitive to the facts that go beyond the financial sphere and therefore pay little attention to them. This mentality is extremely short sighted and ultimately destructive on many levels. Ironically the natural way or sustainable method is often more cost effective and less harmful on the environment. If legislation changed, conventional methods would become too costly to continue and alternative, sustainable methods would be forced into action. The knock on effect would be beneficial to all.
Fortunately, some people are changing things for the better, conservation groups have heightened awareness of the issues and people are taking notice. There is a surge of focus towards sustainable living and a new approach to conservation overall. It is no longer about keeping animals in a fenced natural area, but about conserving natural areas within existing urban areas, joining protected areas with wildlife corridors to facilitate species movement and allow natural process and interactions to occur. Environmental issues are at the forefront of political agendas, and the “greenies” are being heard!
The study of biodiversity is a relatively new science and much is yet to be learnt, so far we can see that it is multidisciplinary; incorporating social, political, biogeography, oceanic and terrestrial ecology. The more we learn and the better we understand the factors and processes contributing to the sustainability of biodiversity the more success we may have in effectively conserving it. Hopefully we will see the error in our selfish ways and realise that it is not a luxury to protect the natural world but a necessity. We need to cultivate and develop a respect for species other than our own because our survival is intrinsically linked with theirs. We cannot forget that we are dependent on the natural world for so much and that by destroying it we ultimately place our own species on the path to destruction.