You are here: / Introduction / Introducing biodiversity

A definition of biodiversity

In the Convention on Biological Diversity signed by many member states at the Earth Summit held in Rio de Janeiro (Brazil) in 1992, explains biodiversity as follows:

"Biological diversity" means the variability among living organisms from all sources including terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems.


Types of biodiversity

Biodiversity is a generic term that can be related to many environments and species, for example, forests, freshwater, marine and temperate environments, the soil, crop plants, domestic animals, wild species and micro-organisms.

Basically it can be classified according to three types of diversity:

Of particular importance are the taxonomically isolated species, as they have little similarity to other species and therefore are unique with respect to their genetic structure. These species are often endemic meaning limited to one specific area. Their extinction would mean a greater loss for global biodiversity rather than just the extinction of a species.


Distribution of Biodiversity in Europe

In Europe, biodiversity is very unevenly distributed with the least variety of ecosystems and lowest diversity occurring in Northern Europe. Centres of high biodiversity are to be found in the Mediterranean (Italy, Spain, Greece, France) and on the fringes of Europe (Bulgaria, Ukraine, Georgia, Armenia, Turkey), with over 5,000 endemic plant species that occur only in these countries. The Mediterranean is Europe's richest sea in terms of biodiversity.


The importance of biodiversity

Biodiversity is often used to draw attention to issues related to the environment. It can be closely related to

  • the health of ecosystems.
    For example, the loss of just one species can have different effects ranging from the disappearance of the species to complete collapse of the ecosystem itself. This is due to every species having a certain role within an ecosystem and being interlinked with other species.
  • the health of mankind.
    Experiencing nature is of great importance to humans and teaches us different values. It is good to take a walk in the forest, to smell flowers and breath fresh air. More specifically, natural food and medicine can be linked to biodiversity.

Example: The importance of biodiversity in the Black Sea

The Black Sea region used to be one of the most important areas for fisheries and for food and income for local people. Sturgeons (Acipenser sp.), mullets (Mugil sp.), and mackerel (Scomber sp.) as well as other species have been extensively exploited in this area. However, human activities related to agriculture, shipping and tourism now exert strong pressure on the environment, especially in the northern part of the Black Sea, and are taking their toll on biodiversity and damaging fish stocks.

Threats to Biodiversity
Large amounts of fertilizers were carried to the sea from agricultural areas along the large rivers, such as Don, Dnepr, and Dnjestr. Oil leaked into the sea from ports on the eastern shores and directly from tankers crossing the Mediterranean. Wastewater from cities and heavily visited coastal tourist towns was discharged without any purification.

Consequences for the ecosystem
All of this leads to pollution and eutrophication meaning the enhanced blooming of planktonic algae due to increased nutrient loads. Planktonic algal blooms lower the water transparency letting only a little amount of light through the water where makrophytes usually grow. This is how the natural belt of bottom vegetation along the Black Sea coast has been destroyed. For example, the vertical distribution range of Cystoseira spp. decreased from 0-10m to 0-2,5m.

The consequences were drastic because the habitat is of major importance as a nursery for spawn and hatchlings of many marine species. This led to a drop in reproduction rates and hence fish stocks.

Sturgeon populations
For the economically important sturgeons, some human activities caused a rapid decline in reproduction rates: All major rivers were dammed for producing hydroelectrical power thus cutting off the migration routes for the sturgeon. This had serious consequences as the fish live in the sea but need to swim up rivers to spawn.

The carnivor jellyfish Mnemiopsis, was introduced to the Black Sea by accident in the early 1980s by ballast water from tankers. This alien species did not have any natural predators in the area and reproduced rapidly forming large populations. Like sturgeon and other fish species the jellyfish feeds on planktonic eggs and larvae. Competition for food became stronger and eventually the jellyfish outcompeted the causing their dimise.

The overfishing and the accidental introduction of the ctenophore Mnemiopsis leydyi in the Black Sea, resulted in the collapse of the pelagic fisheries of the area. The effect of over fishing caused the decline of pelagic fish biomass and the optimal conditions that M. leydyi thrived on in the Black Sea.

The reduced number of planktivorous fish caused the increase of M. leydyi, and the decline of species diversity of mesozooplankton and ichthyoplankton (link to Shiganova, 1998).

The results
The decline in ichthyoplankton affected the commercial fish stocks and therefore the total biomass. As a result the number of commercial fish species was reduced from 48 to 6 and the commercial fish catches declined from 400,000 tons to only 50,000 tons, leaving a collapsed fisheries sector and large unemployment. The loss of fisheries in the Black Sea after the introduction of Mnemiopsys is estimated at hundreds of millions of dollars every year.

The role of ICZM
The ongoing neglect of natural resources and ecological interrelationships resulted in a disastrous development, which can hardly be reversed. In order to restore some of the functions within this old ecosystem, new approaches need to be applied that do not only focus on factors just beneficial to men, but also keep in mind the consequences for other sectors as well.

This site is optimized for viewing with Internet Explorer 4 and higher