Human Influences on Biodiversity

Human Influences on Biodiversity - Key SQA Definitions:

Humans have throughout history had huge impacts on the natural world.  These impacts can be both positive and negative in effects, however, the vast majority of impacts that Humans have had is negative. The impacts usually are accidental (not intentional) but that does not make them any less impactful. 

Negative Human influences on Biodiversity include:- 

The unintended effect of all of these infulences is to reduce biodiversity, reduce or increase species population or cause extinctions. 

Unintentional Influences : Deforestation

Deforestation is the large scale removal of trees and forests, which occurs for a variety of reasons. 

These reasons include:-  

These reasons have been used for thousands of years on a small scale, but due to increases in population and technology, deforestation has increased rapidly over the last century, with clearing land for food being the main reason. 

The graph below shows the drivers of forest loss across the Brazilian Amazon rainforest in a single year (2013). As can be seen, clearing land for farming (especially cattle farming) makes up more than 75% of the deforestation:-

Deforestation has a huge impact on biodiversity by destroying habitats completely and therefore reducing available land that species can thrive in. It is estimated that several hundred species of plant, animal and insect are lost each day partly as a result of deforestation, and this rate is increasing. 

Deforestation Case Study : The Caledonian Forest

The Caledonian Forest was once a vast woodland that covered Scotland. The forest consisted of mainly Scots Pine, Birch, Rowan, Aspen, Juniper, Oak and a few other hardy species. On the west coast, however, Oak and Birch formed a temperate rainforest ecosystem rich in ferns, mosses and lichens.

Remnant of the Caledonian Forest in Glen Affric, Highlands

 The Caledonian Forest formed at the end of the last ice age, around 7,000 years ago, but by the 1600s had been almost completely destroyed through deforestation.  It remains now only in very small pockets of ancient woodland in remote parts of Scotland, which are now protected by law to preserve these remaining areas.

This unique ecosystem is home to some of Scotland's rarest species of plants and animals:-


Scottish Wildcat

Pine Martin


Unintentional Influences : Pollution

As human populations have increased, so has the amount of pollution that is entering the environment. Pollution can come from many sources, and cause damage to a wide variety of ecosystems, sometimes thousands of miles from their source. The diagram below shows some of these sources:-

Land Pollution

Land pollution occurs when waste from industry and homes is not recycled but dumped into landfill sites. Landfill sites are simply big holes in the ground that waste is dumped into then covered over with soil. 

Pollution can spread as chemicals in the waste leak or are blown from the site into the surrounding area. 

Other land pollution occurs when waste is illegally dumped into the environment. 

Water Pollution

Water pollution can occur when waste is dumped directly into waterways or indirectly from chemicals leaching into groundwater from landfill sites.

The pollution can remain in the local area or can flow out to sea, becoming a global issue. 

Pesticides and fertilisers used by farmers to kill weeds or insects and to support plant growth can enter streams and rivers causing water pollution. These chemicals either kill aquatic life or cause increased growth, known as 'Eutrophication'. 

Air Pollution

Air pollution is caused by gases or particulate matter being released, usually through the burning of flammable materials. 

This releases gases such as carbon dioxide that contributes to climate change. It also releases sulfur dioxide and nitrogen oxides which can cause acid rain.

Air pollution can also be caused by tiny particulates from smoke which can cause smog. This smog can cause respiratory problems and is a major health risk in cities around the world. 

Pollution Case Study : Eutrophication

Eutrophication occurs when fertilisers or sewage enters a waterway such as a loch or river, and causes excessive plant and algal growth, causing major changes in the balance of the ecosystem. In severe cases, eutrophication can cause the complete collapse of an ecosystem. 

As can be seen in the above graph, as the nutrient levels in a loch increase, the huge increase of Algae growth comes at the expense of all other aquatic plant life. 

This thick blanket of Algae prevents sunlight from reaching the plant life below the surface, preventing photosynthesis and therefore killing the Pond Grasses and Phytoplankton present. 

When the algae die, their remains are decomposed by bacteria in the water, depleting the oxygen levels in the water, killing aquatic life such as fish.

This completely disrupts the Food Web, with the potential to cause a collapse of the entire ecosystem, leaving behind a dead, empty loch. 

The process of eutrophication can also occur in marine environments:-

Unintentional Influences : Climate Change

Climate Change is having a major impact on food webs and ecosystems globally. As temperatures change, organisms can migrate into new areas as the conditions become more favourable to them. The net effect of this is species movement north in the northern hemisphere. This causes impact on the established ecosystems as new organisms arrive and others leave an area. 

An example of this is Asian Tiger Mosquito, which is responsible for transmitting Malaria. In the early 2000s, the mosquito could only survive in the far south east of the mainland US, but if climate change continues, it is predicted that the Mosquito will be able to survive across most of the central and eastern US, placing millions more people at risk of Malaria:-  

Unintentional Influences : Over-exploitation

Over-exploitation occurs when a plant, animal or physical resource is harvested at a rate that exceeds the reproduction of the plant and animal species or the replacement of the physical resource. 

By over-exploiting a species, that species will show a rapid decline in numbers and in severe cases become extinct. 

An example of overexploitation is the collapse of the Plains Bison population in North America. Before the arrival of Europeans, there was an estimated 60 million Bison, being sustainably managed by the Indigenous American population. 

By the end of the 19th century, however, this Bison population had crashed to only 512 individuals due to a combination of market demand for meat, as well as a deliberate effort by the US Government to wipe out the the bison in order exert control over the Indigenous population (due to their heavy reliance on Bison). 

Pile of Bison Skulls at a fertiliser plant in 1892

By 2016, due to conservation efforts, the number of Bison in North American had gradually climbed up to about 20,000 individuals. 

Bison conservation is important as the Plains Bison is a 'Keystone Species'. A keystone species is a species which define an entire ecosystem, having an effect on all parts of it. 

When the Bison grazes on grasses, they do this to a range of sizes, creating a range of habitats for small mammals, insects and birds. Through their dung, seeds of plants are spread and existing plants are fertilised. The hooves of the Bison break up the soil, allowing oxygen to penetrate deeper and cycling nutrients to the surface. 

The Bison also roll to clean themselves, causing depressions called wallows to form. The soil in these wallows is compacted and water cannot pass through it, so when it rains these wallows fill with water. These water filled wallows provide additional habitats for amphibians and birds as well as drinking water for a range of species.

Intentional Influences : Ecological Engineering - Biological Control

Humans have intentionally made changes to ecosystems which have had damaging consequences. In the early 1930s, Sugar Cane plantations in Australia were experiencing crop damage due to the Grey-backed Cane Beetle. In order to reduce the population size of the Cane Beetle, a non-native species of Toad (South American Cane Toads) was introduced to eat the beetles. Using one organism to manage the population of another in this way is known as 'Biological Control'. 

The Cane toads did nothing to reduce the Cane Beetle population but reproduced very quickly and given their size, quickly outcompeted native amphibians for food. As the cane toads are also poisonous, any predators such as foxes that tried to eat them died. 

This combination of outcompeting other amphibians for food and killing predators has caused massive damage to the native ecosystems in the areas the Cane toad is present. The introduction of the Cane Toad has been linked extinction of several native predator species in Northern Australia, including the Northern Quoll (a small marsupial). This territory is set to expand further due to climate change:-

Biological control methods do have their place in modern ecological management, provided that it is very carefully planned, understood and implemented. For example, the use of moths to control the spread of Cactus in Australia has been very successful. 

Prickly Pear Cactus

Cactus Moth Larvae eating Cactus

Prickly Pear Cactus was introduced into Australia in the mid 1800s to be used as a drought-resistant source of cattle feed and for use in hedges on property boundaries. However, the Prickly Pear soon established itself as a rapidly growing invasive plant that blanketed the ground preventing the growth of any native plants. This reached a point when farmland became unusable, covering 93,000 square miles of New South Wales and Queensland. 

Many methods were attempted to clear the cactus by physical or chemical means, but nothing worked. In the end, in the mid 1920s,  it was decided to attempt to use a biological control - Cactus Moths. 

Cactoblastis Cactorum moths are indigenous to a small area of Argentina and their larvae rapidly eat their way through huge volumes of prickly pear cactus.

The moths were tested on a range of plants to ensure that the moths did not attack native plants and were then released into the infested areas. 

By 1933 it was estimated that 80 per cent of the infested land in Queensland, and 50–60 per cent in New South Wales, had been cleared.

Intentional Influences : Ecological Engineering - Reforestation

Reforestation is the process of replanting trees and forests that have been cut down. There are two main types of reforestation activity:-

Urban Reforestation

This consists of planting trees within an urban setting. Urban reforestation increases shady areas, protects against heat buildup, produces green spaces for leisure, and improves air quality. 

Rural Reforestation

This consists of planting trees within a rural setting. Rural reforestation is used to replace forests previously removed for timber, to reduce soil erosion by providing stability, reduce the effects of flooding in an area and to preserve or regenerate biodiversity.

Reforestation supports the biodiversity of an ecosystem by replacing lost habitats, and preventing the felling of virgin forests by providing a more sustainable source of wood for industry. 

However, just like other forms of Ecological Engineering, if reforestation is not fully thought out and well implemented, it can cause futher issues:- 

Intentional Influences : Ecological Engineering - Rewilding

Rewilding is defined as the large-scale restoration of ecosystems by full ecological management. 

Rewilding involves:- 

An example of rewilding in Scotland can be seen within Creag Meagaidh National Nature Reserve in Northern Scotland. 

This region of Scotland had been overexploited for forestry, Deer and Sheep farming for centuries. The ecosystem had lost almost all of its native tree cover due to overgrazing, and the loss of habitats had severely reduced biodiversity. Without natural predators, the Deer population was too large, leading to over-grazing and other environmental damage. 

In the mid 1980s, a program of Deer Control measures were put in place to reduce deer numbers within the area. These control measures included Deer Fencing to prevent access, issuing Deer Stalking permits and in some cases systematic Deer Culling to directly reduce numbers. 

Over the last 40 years, the reduction in Deer population has allowed the recovery of the native plant species, with tree coverage increasing without the need for planting, as well as the return of many plant species that used to be present. The increased plant and tree cover has allowed an increases in the variety of habitats  and therefore has shown a marked increase in local biodiversity. 

Low biodiversity Scottish landscape due to overgrazing by Deer and deforestation

High biodiversity Scottish Landscape after implementing Deer Control measures 

Indicator Species

An indicator species is an organism whose presence or absence, as well as abundance, in an ecosystem can be used as a measure of healthy an ecosystem is. Different species are capable of survive or thriving in different conditions (see eutrophication above) so by monitoring certain species, an understanding of the ecosystem can be gained. 

An example of an Indictor Species (or group of species)  is Lichen. Lichen are not one organism, but actually a type of symbiotic relationship between algae and fungi. They work together to provide each other with the nutrients that alone neither could access. 

Lichens are sensitive to air pollution such as nitrogen and sulphur compounds from vehicle exhaust because they receive all their nutrients and water from wet and dry atmospheric deposition due to the lack of a root system. The higher the air pollution, the more deposition will occur, with too much damaging or killing the Lichen. 

Some species of Lichen can withstand higher levels of pollution than others, so the type of Lichen found as well as abundance is useful as a Indictor of Ecosystem health:-

'Bushy' Lichens

'Bushy' or 'Beard' Lichens, such as Usnea, form mini bushes or tassels attached onto the bark of tree trunks and branches. They can only survive in areas with very low levels of air pollution, so are mostly found in isolated woodlands. 

'Leafy' Lichens

'Leafy' Lichens, such as Parmelia, form leafy structures close to the bark or rock they form on. They are more tolerant of air pollution, but still cannot survive high levels.  

'Crusty' Lichens

'Crusty' Lichens, such as Caloplaca, form crusts on the surface they form on. Crusty Lichens are the most tolerant of air pollution, and can be found in inner city area with very poor air quality.

Conflicts between Stakeholders 

Humans use the natural environment for a range of uses (such as farming, logging, leisure etc.) but not all of these uses are compatible with each other. When two uses of the environment are not compatible with each other the people wishing to implement them (the stakeholders) can come into conflict. This conflict usually takes the form of political and social arguments, but in severe cases can lead to full physical conflict. 

One of the most common conflicts in land use within Scotland is between Farmers and Tourists. Especially during the summer months, tourists visit rural areas of Scotland for a wide range of leisure activities, for example hiking, camping, sailing, or adventure sports. 

These activities can bring these tourists into conflict with the farmers or rangers managing the land.  Some of these conflicts  (and their possible solutions) include:-

Stakeholder Conflict Case Study : Fishing Vessels in UK waters

The Scallop beds around the UK Crown Dependency islands of Jersey and Guernsey (14 miles off the French coast) have been the source of stakeholder conflict between the UK and France. This has been due to changes in Fishing Licenses caused by Brexit. These licenses allow fishing boats from France (or the rest of the EU) to enter British territorial waters for fishing purposes. 

The map below shows the territorial waters claimed by the UK (Blue Line) and the most lucrative Scallop fishing areas (in red):-

In November 2021, French fishermen felt that they were unfairly being denied these licenses and therefore access to fishing grounds and staged protests at sea. When that did not make a difference, they began to blockade French ports, preventing British vessels landing their catch. There were also incidents at sea, where boats jostled for good fishing spots, causing collisions as well as rock and firework throwing between the  French and British vessels. 

As of April 2023, there has been some progress in issuing further licenses, and a compensation scheme has been set up by the European Commission to assist fishermen who waiting for permits. However, the base issues are yet to be fully resolved. 

Stakeholder Conflict Case Study : Humans & Elephants 

Stakeholder conflict is not limited to Human-Human interactions. Human and Animals can also come into conflict when animal habitats are infringed on by expanding Human communities.

An example of this can be seen Between Humans and Elephants in India and South-East Asia. Elephants are found across South-East Asia, and where there habitats intersect with Human communities, due to the Elephants large size and foraging habits, conflict can occur. 

Due to deforestation for either timber or additional farmland, the habitat of the Elephant is being greatly reduced over the last 100 years. This has led to more Elephants entering populated areas in search of food, coming into conflict with the people present.  

A single Elephant can eat up to 450kg of plant material a day, so with an average herd size of around 7, a family group can consume over 3 tonnes of food per day. This means that a group of Elephants can quickly consume entire smallholder farms in they enter the farmland. 

Farmer's livelihoods depend on their farms, so they defend them vigorously. As Elephants are huge animals, they can overcome most barriers put in their way, so noise defenses (such as banging metal sheets) or fire are used to drive Elephants away from farmland.

Elephant and Calf being attacked by a crowd using burning tar in Northern India

Poisoning of Elephants in Palm Oil Plantations

This has led to further losses to the Elephant population due to injuries sustained in physical conflicts with humans. Every year, people are injured and killed due to conflict with Elephants across South East Asia, with 100s killed in India annually. 

However, even though the number of Elephants has remained fairly constant over the last decade, the number of human fatalities due to Elephants in India has dropped by more than a third:- 

This is due to work being done between the farmers, government agencies, charities and other stakeholders to tackle the issue of Human- Elephant conflict.

Changes that have been made at the local farming level include:- 

Monitoring and Governing Human Influences on Biodiversity

In order to monitor, assess and regulate the Human Influences on Biodiversity, countries around the world have dedicated organisations who are responsible for overseeing this. 

In Scotland, there are two main organisations with a remit for this:- 

The Role of SEPA

The Scottish Environmental Protection Agency are Scotland's governmental organisation in charge of regulating Human interactions with the Environment. SEPA's role is to make sure that the environment and human health are protected and to ensure that Scotland’s natural resources and services are used as sustainably as possible as well as contribute to sustainable economic growth. 

This incudes delivering Scotland's flood warning system, working with the Scottish Government to deliver Scotland’s Zero Waste Plan, operating the Scottish aspect of the Radioactive Incident Monitoring Network and work with the Health and Safety Executive to control the risk of major accidents at industrial sites. 

The Role of NatureScot

NatureScot is the lead public body responsible for advising Scottish Ministers on all matters relating to the natural heritage.

The aims of NatureScot are:-

NatureScot also advise local authorities and work with the Scottish Parliament and public, private and voluntary organisations towards these shared aims. 

NatureScot is also responsible for designating and protecting 'Sites of Special Scientific Interest' (SSSIs). SSSIs are areas of land and water that are considered to best represent the natural heritage of Scotland. 

This can be in terms of:

It is an offence for anyone to intentionally or recklessly damage the protected natural features of an SSSI, and it is one of the roles of NatureScot to monitor and enforce this through prosecutions where neccessary.