The world around us varies greatly. On a ten-minute walk, you will pass a range of different ecosystems - trees, hedges, perhaps a pond or a field. Even within the small island of the UK, there is substantial variation - from the bleak moors in Devon to cold forests in Scotland. Why does it differ so much? Well, the answer is due to ecosystem diversity.
Ecosystem Diversity Definition
Ecosystem diversity is the variation between different ecosystems, including their effects on the rest of the environment and on humans.
Fig.1. A landscape image showing the possible diversity within a land ecosystem: the plains with grass and the wide river, plus the forest border with a smaller river width.
An ecosystem comprises the organisms that live in an area, the interactions between each other and the natural environment.
Ecosystems can be either aquatic or terrestrial, filling the oceans and covering the land. Their size can range from the Sahara Desert or the Pacific Ocean, right down to a singular tree or lone rock pool.
Example of Ecosystem Diversity
There are many examples of ecosystems: the Sahara desert, the Amazon rainforest and the Niagara falls are examples of the diversity of ecosystems we can find on planet Earth. At the same time, ecosystems are connected within larger biomes.
Biomes are major life zones, classified according to their vegetation type or physical environment.
A few major biomes are summarised below.
Tropical forests: vertically layered forests compete for sunlight. Temperature, rainfall and humidity are high. These forests support incredibly high levels of animal biodiversity.
Tundra: high winds and low temperatures restrict plant growth to herbs and grasses. Many animals migrate elsewhere for winter.
Desert: low precipitation limits plant growth. Temperature can vary considerably, exceeding 50℃ in the day and reaching -30℃ at night. Animal biodiversity is low, as few species are adapted to these harsh conditions.
Open ocean: constant mixing by currents promotes high oxygen levels and low nutrient conditions. Phytoplankton and zooplankton dominate, providing an important food source for fish.
Grassland: precipitation and temperature vary seasonally. Grasses dominate, fed on by large grazers.
Coral reefs: corals thrive in waters with high temperatures and oxygen availability. These animals provide a carbonate structure, supporting an incredibly high diversity of fish and invertebrates. Coral reefs are considered to be on par with tropical rainforests regarding animal biodiversity.
Biomes have unique features shared by all ecosystems within them. However, ecosystems can vary even within biomes. Take deserts for example. The hot, arid Sahara we mentioned above might spring to mind. However, deserts can be diverse places:
| Desert | Abiotic Conditions | Landscape | Animals & Plants |
| Sahara Desert, Africa | Hot, dry, strong winds | Sand dunes | Palm trees, cacti, snakes, scorpions |
| Gobi Desert, Asia | Cold temperatures, snowfall | Bare rock | Grasses, gazelles, takhi |
| Antarctica | Freezing temperatures | Ice sheet covering bare rock | Mosses, birds |
Table 1. Different types of desserts and their characteristics.
But what causes the differences between these deserts?
Factors Affecting Ecosystem Diversity
Ecosystem diversity has different factors that affect it directly. These factors can be traced back to niches. Every species in an ecosystem has a different niche. Specific niches, combined with varying conditions around the globe, result in heterogeneous species distributions (i.e. uneven distributions of animals and plants). This results in different community structures, and thus different ecosystems.
A niche is the specific set of resources that an organism uses in its environment. These can be abiotic (such as temperature), or biotic (such as the food it consumes).
Climate and Geography
Climate patterns are mostly determined by the availability of solar energy and the movement of the Earth. The climate varies depending on the latitude and the time of year.
Latitude can affect seasons. Regions between 20°N and 20°S have tropical climates - wet/dry seasons with high temperatures year-round. Regions further from the equator experience summer/winter with significant temperature differences between seasons.
Ocean currents can influence the climate of coastlines by heating and cooling.
The Gulf Stream is a warm Atlantic Ocean current that influences the climate of western Europe. Winter air temperatures can be up to 10°C warmer than equivalent latitudes, hence why the UK has milder winters than the northern states of the USA. Climate change has the potential to weaken the effect of the Gulf Stream. Just a small reduction in the current's heat transport could result in a considerable cooling effect across western Europe and the UK.
Mountains can affect the climate of an area. When air flowing in from the sea meets mountains it travels upwards, cools, and releases water as precipitation. Less moisture remains in the air after reaching the leeward side. This rain shadow can create desert-like conditions on the other side of the mountain range.
Furthermore, mountains affect temperature. A 1000m rise in elevation is associated with a temperature drop of 6°C. Sunlight levels also differ depending on the location of the mountain range.
Zonation
Aquatic ecosystems are characterised by the stratification of light and temperature. Shallower water has higher temperatures and light availability than deeper water.
| Zone | What is it? |
| The Photic Zone | The top layer of water, closest to the surface. There is sufficient light for photosynthesis, so biodiversity is at its highest. |
| The Aphotic Zone | The zone beneath the photic zone, which lacks sufficient light for photosynthesis. |
| The Abyssal Zone | A zone found in deep oceans, below 2000 m. Only specialised organisms adapted to low temperatures and light levels can inhabit this niche. |
| The Benthic Zone | The zone found at the bottom of all aquatic ecosystems. It is made up of sand and sediments, and is inhabited by organisms that feed on detritus. |
Table 2. The different zones of aquatic ecosystems.
Interactions between Organisms and their Environment
Multiple factors can limit the distribution of a species within an ecosystem.
Biotic Factors affecting Species Distribution in an Ecosystem
- Dispersal: movement of individuals away from their area of origin or an area of high population density.
- Other species: parasitism, predation, disease, competition (niche is already occupied).
Parasitism: an interaction where a parasite exploits resources from a host, harming it in the process.
Predation: an interaction where a predatory species kills and eats a prey species.
Disease: an abnormal condition affecting an individual's structure or function.
Competition: an interaction where individuals of different species compete for a limiting resource.
Abiotic Factors affecting Species Distribution in an Ecosystem
- Chemical: water, oxygen, nutrients, salinity, pH, etc.
- Physical: temperature, light, moisture, soil structure, etc.
Disturbances
When talking about ecology, a disturbance is a change in a change in the environmental conditions. They are temporary, but can cause significant changes in the ecosystem. Disturbances can be natural (storms, fires, cyclones, volcanic eruptions, etc.) or human (deforestation, mining, land use change, climate change). Frequent disturbances lead to patchy biomes and limited biodiversity.
Fig 3. Climate change increases the frequency of forest fires, as droughts and high temperatures dry out vegetation, making it easier to ignite.
Types of Ecosystem Diversity
As we've mentioned above, there are many types of ecosystems that are contained withing a variety of biomes. But how do we measure the diversity within an ecosystem?
Genetic Diversity
Genetic diversity measures the individual variations of genes within and between populations. A species or population with low genetic diversity faces an increased risk of extinction.
Fig 4. Bananas have low genetic diversity, making them susceptible to stress and disease.
Species Diversity
Species diversity is a measure of the number of species that are present within an ecosystem. Biomes that support a high species diversity include coral reefs and tropical rainforests. Ecosystems with a high species diversity tend to be more resilient because they have a high response diversity (this will be explained in a bit!)
Ecosystem Diversity
The species and environmental factors vary between different ecosystems. Overall functioning should also be considered when analysing ecosystem diversity. The loss or extinction of one species can have knock-on effects on other species present. For example, flying foxes (a species of bat) are important pollinators in the Pacific Islands. Loss of flying foxes could have major effects on other species of that region: flowering plants would have lower reproductive success. Animals that feed on flowers will decline; the whole food web would be affected. Humans would also struggle to pollinate their crops.
Importance of Ecosystem Diversity
Ecosystem diversity is essential for the survival of all species, including humans. Without that diversity, ecosystems become more vulnerable to severe change or extinction, which can have a butterfly effect on other regions. Without healthy environments, neither plants nor animals (including humans) can survive.
Ecosystem Resistance and Resilience
Ecosystem resilience is the amount of disturbance that a system can tolerate while undergoing change to sustain the same functions. A high biodiversity results in a high response diversity, which is critical to resilience.
Response diversity is the reactions to environmental change among species which contribute to ecosystem function.
Ecosystem resistance is the ability of an ecosystem to remain unchanged after disturbance. Like resilience, resistance is highest in diverse ecosystems. For example, ecosystems with a higher diversity are typically less affected by invasive species.
Humans and Ecosystem Diversity
Diversity provides valuable ecosystem services to humans. These can be split into four subtypes.
Provisioning services provide physical resources, such as food, medicine or natural resources.
Cultural services provide recreation, fulfilment and aesthetics.
Regulating services provide amelioration of negative effects, such as tsunamis or pollution.
Supporting services underpin all the others, such as nutrient cycling and photosynthesis.
I hope that clarified ecosystem diversity for you. Remember that an ecosystem comprises of living organisms, and their interactions with each other and the environment. Ecosystems can vary due to climate, interactions and disturbances.
Ecosystem Diversity - Key takeaways
- Ecosystem diversity is the variation between different ecosystems.
- Ecosystems can be part of larger biomes, such as tropical forests, coral reefs and grasslands. Even within biomes, there can be significant variation between different ecosystems.
- The main reasons for variation between ecosystems include climatic conditions, disturbances, and interactions between organisms and their environment.
- Diversity can be measured at genetic, species and ecosystem levels.
- Diversity is important as it helps to maintain the resistance and resilience of ecosystems. It also provides valuable resources to humans known as ecosystem services.
- Jamie Palter, The Role of the Gulf Stream in European Climate, The Annual Review of Marine Science, 2015
- Melissa Petruzzello, What Would Happen If All The Bees Died?, 2022
- Michael Begon, Ecology: From Individuals to Ecosystems, 2020
- National Geographic, Encyclopedia, 2022
- Neil Campbell, Biology: A Global Approach Eleventh Edition, 2018
- Thomas Elmqvist, Response diversity, ecosystem change and resilience, Frontiers in Ecology and the Environment, 2003
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