Definition

The word habitat comes from the Latin verb habitāre, meaning “to live in a place,” and is the frequentative form of habēre, meaning “to have or to hold.” One of the most commonly cited definitions of habitat is from the Convention on Biological Diversity, according to which habitat is a place or type of site where an organism or population naturally occurs. Degradation is a process by which something changes to a worse condition. Hence, habitat degradation is a process by which habitat quality deteriorates and which poses one of the main threats to biodiversity.

Introduction

Over the past decades, we have been witnessing a deterioration in the quality of the environment, the depletion of natural resources, and natural disasters all becoming more frequent. Ecosystems have been significantly changed over the last 70 years; nearly every ecosystem has been impacted by human activity. Humanity faces a shared responsibility for growth in accordance with the principles of sustainable development aimed at preserving the planet’s resources and a healthy environment for future generations.

By the end of the period during which countries’ development policies were formulated in accordance with the Millennium Goals, the UN had established a new agenda that would align development with the principles of sustainable development in the coming years. Sustainable Development Goals Target 15.5 focuses on actions aimed at reducing the degradation of natural habitats and halting the loss of biodiversity and extinction of species (UN 2015). The aim is to conserve ecosystems and promote their sustainable use.

In the biological and environmental science literature, a habitat is associated with a space where an organism or population lives. It is not uncommon for the terms “habitat” and “biotope” to be equated. However, habitat is a wider concept, which refers not only to a space with nonliving matter and energy but also the living community that is located in that area (Lakušić et al. 2015). By its very essence, the concept of habitat as defined here has the same meaning as the term ecosystem. Ecosystem diversity is often identified with the diversity of vegetation. A habitat is defined by the type of vegetation, hence the connection between the terms ecosystem and habitat.

The structure of an ecosystem has a strong influence on the physical processes (fire, floods, erosion) and chemical processes that determine a habitat. Changes in the species composition in communities affect biogeochemical cycles by changing the quality of organic matter, nutrient uptake, hydrology, erosion, fires regime, food web, and other processes.

There is a link between ecosystem stability and biodiversity. Stable ecosystems tend to have a greater diversity and are much more resilient to disturbances. However, prolonged stress, especially anthropogenic pressures, impairs ecosystem stability and functionality and prevents it from returning to a stable state.

Ecological succession is a process of changes in co-occurring species composition subsequent to natural or anthropogenic disturbances in one habitat over time (Morin 2011). With progressive succession, a community becomes more complex and contains more species, while with retrogressive succession, it becomes simpler, containing a smaller number of species (Pidwirny 2006). Retrogressive succession is rare in nature, but it frequently occurs after anthropogenic disturbances.

Habitat degradation causes habitat quality reduction, which can render a habitat less suitable for some species and eventually lead to their extinction. Because of a time lag between events causing habitat degradation and species extinction, it is possible to underestimate the degree of threat to biodiversity (Hanski 2011). The delayed response of species to habitat change can be identified as extinction debt (Tilman et al. 1994).

The functioning of the biosphere is based on nutrient cycling and the flow and transformation of energy in an ecosystem. Therefore, the connection between living things and the functioning of an ecosystem is crucial to the stability of the entire biosphere and represents the link between diversity, ecosystem functioning, and stability (Lakušić et al. 2015).

Biodiversity is increasingly exposed to pressures, while threats to wildlife are becoming numerous, with few indications of change in the days to come. Direct pressures to biodiversity loss include habitat change, overexploitation, pollution, invasive species, and climate change (Pereira et al. 2012). All these pressures are fundamentally the consequence of population growth, consumption and production patterns, and energy use, which can be perceived as indirect drivers. In this chapter, the main causes and pressures of habitat degradation will be discussed in addition to some of the measures that can be applied to mitigate the main causes of habitat degradation.

The Main Pressures and Threats to Terrestrial Habitats

Natural disturbances are initiators of vegetation succession, and high floristic diversity is often the result of natural disturbances since they have a positive effect on nutrient cycling and primary production. However, human activities increase the incidence and intensity of a disturbance and cause profound and frequently lasting changes to ecosystems (Smith and Smith 2012). Several major habitat pressures are directly and indirectly anthropogenically conditioned, and they will be discussed in the subsequent sections.

Agriculture

Agriculture has always been an activity on which a country bases its economic growth. However, the spread of agricultural land at the expense of natural ecosystems has a negative impact on the species and habitats. For example, agriculture is the main driver of deforestation in the tropics. Many agricultural techniques lead to environmental pollution and the overuse of natural resources. Nearly 70% of anthropogenic N2O emission comes from agriculture, and 70% of water withdrawals is used for agriculture (MEA 2005). Techniques aimed at increasing food production can cause habitat degradation. For example, the plowing of cultivated agricultural land renders the soil vulnerable to erosion. Another case in point is the application of fertilizers which have a negative impact on water quality.

Eutrophication is the enrichment of water with nutrients, resulting in an increased primary production and a decreased amount of dissolved oxygen in water, and is considered one of the important factors of habitat change (Glibert et al. 2005). It increases the production of phytoplankton and macrophytes and facilitates the thriving of cyanobacteria (Pereira et al. 2012). Eutrophication and other ecosystem changes resulting from pollution are one of the main drivers of habitat degradation (Pereira et al. 2012).

Agriculture and habitat pollution are closely related. As already mentioned, the excessive application of fertilizers is a serious environmental concern resulting in fertilizer runoff. Nutrients and other chemicals that are washed away from an agricultural land contaminate the groundwater, surface water, and soil of adjacent areas. Besides rivers, lakes, and ponds themselves, the marine ecosystem can become eutrophic due to the pollution from domestic and industrial sewage and from the inflow of polluted rivers.

Agriculture is also the main cause of eutrophic soil. Current techniques are especially harmful when an initially nutrient-poor soil is converted into a fertile one. That induces a change in species composition since species adapted to nutrient-poor soil are replaced by species adapted to a nutrient-rich habitat. The new conditions especially favor invasive species which are better adapted for nutrient-rich sites and thrive more than native species (Daehler 2003). Similarly, when used for fish farming, lakes, ponds, and reservoirs are polluted with excessive nutrient loading. Often, this will lead to an increase in the number of exotic species, which further maximizes the likelihood of invasive species expansion (Fig. 1). All these changes can have a negative effect on other aquatic biota and birds.

Fig. 1
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Nutrient enrichment from agricultural runoff promotes the growth of invasive plants Reynoutria japonica and Symphyotrichum lanceolatum. 28 Sept. 2016. (The authors’ personal collection)

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Drainage and soil amelioration aimed at creating agricultural land are the main drivers of change in mires, bogs, and fens. This can carry serious implications since the loss of water diminishes the cleansing capacity of wetlands. Eutrophication of land and water is also a factor in endangering wetlands. Wetlands are ecosystems permanently or temporarily flooded by water and are very diverse in nature (Matthews 1993). Agricultural runoff introduces nutritional enrichment which can change the floristic composition of wet habitats. Observers have noticed that agricultural runoff promotes the availability of nitrates and phosphates that increase the competitive ability of Common reed (Phragmites australis) and Great manna grass (Glyceria maxima), which become dominant plants in those communities (Sefferova et al. 2008).

Pastures are habitats used for grazing cattle and sheep, and, if well managed, they are considered to be highly productive for a habitat. Their vegetation is usually comprised of grasses, forbs, and legumes. Agricultural management practices are typically cited as reasons for pasture degradation. Cattle overgrazing, for example, can lower the productivity of these habitats (Beeby and Brennan 2008). It reduces floristic diversity and native plant populations since they are more sensitive to disturbance. Further, overgrazing can contribute to organic matter depletion, soil compaction, erosion, and changes in microorganism communities. All these changes have a negative effect on species diversity and facilitate the transformation from high-productivity to lower-productivity habitat. Similarly, frequent mowing of pastures leads to a decrease in floristic diversity, since it prevents herbaceous species from flowering and seed setting. In contrast, low-intensity grazing can facilitate vegetation successions which result in the transformation from grass-dominated to shrub-dominated vegetation (Beeby and Brennan 2008). Another practice that affects productivity is the increasing use of invasive plants as pasture plants to boost livestock production. In addition to reducing species diversity of such pastures over time, invasives are the source of other environmental problems due to the high risk of their escape to natural habitats (Driscoll et al. 2014).

Deforestation and Monocultures

Forests play an important role in mitigating climate change in their capacity as carbon sinks. Deforestation is defined as the permanent or temporary removal of forests for agricultural or other uses (Hassenzahl et al. 2017) and is a major direct and indirect cause of extinction of today’s species. It has been projected that by 2100 up to 21% of Southeast Asian forest species will have been lost to continuous deforestation (Sodhi et al. 2009). Consequently, the objective of Target 15.2 is to promote sustainable management of forests, halt deforestation, restore degraded forests, and increase afforestation and reforestation (UN 2015).

One estimate shows 80% of global deforestation is caused by agriculture. In Latin America and (sub)tropical Asia, timber extraction and selective logging are the leading causes of forest degradation, while in Africa fuelwood collection and charcoal production are the main drivers of forest degradation (Kissinger et al. 2012). The same authors find mining as another factor in forest degradation in Africa, (sub)tropical Asia, and Latin America while urban expansion especially contributes to forest degradation in Asia.

Deforestation causes drastic changes in habitats since keystone species that maintain the community structure and define the whole ecosystem are removed. Specifically, logging drives changes in nutrient cycling in all forest habitats and affects the physical and chemical properties of soil. Inappropriate management practices, such as unsustainable cutting and total removal of dead trees, result in forest degradation and biodiversity decline. When it comes to logging methods, forest disturbance varies in intensity per approach. In selection cutting, only mature single trees or small groups of trees are removed. The result is simply gaps in the canopy, and disturbances are smaller compared to clear-cutting (Smith and Smith 2012). However, selection cutting impacts species composition since it brings about changes in a habitat’s living conditions (Smith and Smith 2012). In contrast, clear-cutting causes habitat destruction and transforms the remaining habitat into a low productive one. After any deforestation, the soil becomes more vulnerable to erosion. Due to a lack of vegetation, the upper layer of soil can be easily removed by wind or water. This is particularly pronounced in habitats with sloping land. Soil erosion has the potential to cause sediment pollution in habitats near streams, rivers, and lakes, which can bear negatively on natural processes in aquatic ecosystems.

In order to satisfy the growing demands of the human population, high-yielding monocultures are becoming more and more frequent. Modern agriculture and forestry lead to biotic homogenization. Many of today’s natural forests are being degraded and transformed from species-rich forests to habitats with limited biodiversity. The ever-increasing demands for industrial wood, fuelwood, and fiber have converted natural forests to plantations of fast-growing trees, which are often exotic species of little biodiversity value.

Urbanization

Population statistics show that in 1950, 30% of the world’s population lived in urban areas. Today, that percentage has gone up to 55, and it is expected that by 2050, 68% of the world’s population will be living in urban areas (UN 2018). Urbanization can cause complete destruction of ecosystems. The urban land expansion increases the pressure on biodiversity leading to habitat loss and fragmentation (Fig. 2). It is not uncommon for human settlements to be located near vulnerable ecosystems, such as wet habitats, with the resulting habitat degradation due to drainage.

Fig. 2
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Urban expansion drives habitat degradation by modifying habitat hydrology, soil biochemistry, and species composition. 30 Sept. 2018. (The authors’ personal collection)

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Urban and suburban zones are the centers of the spread of invasive species. From these zones, invasive species continue their expansion into rural areas. Urbanization affects species richness and species composition. It has been shown that nonindigenous plants, butterflies, and birds increase in abundance while the number of indigenous species decreases in urban and suburban zones (McKinney 2002). In addition, changes in land use, particularly fragmentation, cause ecosystem disturbances and create corridors for propagule dispersal, thereby promoting species invasion. Borgmann and Rodewald (2005) point to a positive correlation between the percentage of urban land cover within 1 km of riparian woodland and the percentage of invasive Amur honeysuckle (Lonicera maackii) and Tatarian honeysuckle (L. tatarica) cover. In addition, forests near urban land are susceptible to invasion of alien species because of the high use of ornamental plants which are sources of propagules.

Recreation and Tourism

Pressure from recreation and tourism has strong implications for habitat structure and species composition. The negative effects are associated with a large number of visitors, their activities, and tourism infrastructure. In addition to tourism in urban and suburban areas, tourist visits to natural habitats and ecosystems with restricted distribution or protected areas can have a significantly negative impact on biodiversity. Given that protected areas often provide habitat and protection for vulnerable, endangered, or critically endangered species, tourism can inflict irreversible damage. The development of tourism and associated infrastructure can cause changes in species composition, chemical pollution, overuse of resources, soil degradation, noise, litter, and deforestation (Fig. 3). Even though tourism infrastructure does not occupy large areas, its effect on the habitat can be significant and permanent (Pickering and Hill 2007). Besides accommodation infrastructure, transport infrastructures such as roads, tracks, trails, and lookouts can be stressors to biodiversity. Activities such as trekking, skiing, snowboarding, rock climbing, mountain biking, motorbike expeditions, canyoning, golfing, and horseback riding can affect resident species. Large areas of Mediterranean sand dunes have been degraded by tourists causing damages to early stages of plant succession (Beeby and Brennan 2008).

Fig. 3
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Negative impacts of tourism development in biodiversity-rich areas. Species composition and diversity are altered by the development of tourism infrastructure, which results in habitat degradation. 30 Sept. 2018. (The authors’ personal collection)

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Further, skiing activities are potential threats to mountain habitats. In terms of recreational activities, skiing and ski piste preparation have the greatest impact on alpine habitats. Those activities affect species composition, diversity and productivity of vegetation, and soil properties (Wipf et al. 2005). According to Wipf and colleagues, snow-grooming vehicles, machine-grading, and systems for artificial snowing cause the most damage. Snow-grooming vehicles and machine-grading are a source of mechanical damage to plants and upper layers of soil, while artificial snowing systems cause an increase in soil moisture, altering species composition. Further, snowmaking machines use a large amount of water which comes from surface water which contains high concentrations of nutrients and thus increases soil nutrient load during snowmelt.

Energy Production

Quarries and surface mining are major factors in habitat destruction and degradation (Fig. 4). Quarries are often located near refugium habitats, which are host to a large number of endemic and relict species. In addition to their direct impact, quarries increase noise and dust pollution in the surrounding habitats. Besides contributing to habitat loss and destruction, open-pit mining is problematic due to the generated byproducts such as waste rock and tailings, which need to be hauled to waste dumps and tailings dams (Fig. 5). Waste dumps and tailing dam are sources of pollution and can present a serious risk to adjacent habitats (Fig. 6).

Fig. 4
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Habitat degradation caused by open-pit mining. Negative effects, such as biodiversity loss, pollution, changes in plant communities, deforestation, etc., will occur at a great distance from the exploitation site. 01 Oct. 2009. (The authors’ personal collection)

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Fig. 5
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Handling and disposal of tailings cause destruction of ecosystems. Large quantities of tailings can contaminate land, water, and air and present serious threats to the natural environment. 05 Aug. 2009. (The authors’ personal collection)

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Fig. 6
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Utilized ash being dumped onto a large area causing habitat destruction, degradation, and pollution. Fly ash can be deposited on topsoil or surface water, causing soil and water chemical changes and affecting species in surrounding habitats. 17 Dec. 2006. (The authors’ personal collection)

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Another potential source of habitat degradation is the production of gas and oil, as well as renewable energy. After reviewing the literature concerning this issue, Jones et al. (2015) list wildlife mortality, habitat loss and fragmentation, and noise and light pollution among major effects of gas, oil, and wind energy production on biodiversity and ecosystem services. For instance, energy production can cause wildlife mortality. The most common occurrences are avian mortality from collisions with wind turbines and power line electrocutions. The authors point out that the synergistic effect of wind energy production with other anthropogenic impacts may be the cause of avian and bat population declines. Noise and light pollution from turbines, roads, drill rigs, flares, and construction equipment can lead to a decline in the wildlife population. In addition, reserve pits and evaporation ponds used in the process of oil and natural gas production can likewise be sources of pollution.

Climate Change

While it is predicted that climate change will be the main driver of biodiversity change by the end of the century, ecosystems are already showing the effects of climate change (MEA 2005). Statistics show that the Earth’s land and ocean temperature has increased by 0.85 °C since 2012 (IPCC 2014). According to the IPCC Report, temperatures are expected to increase if the current rate of greenhouse gas emission persists. Climate models predict rises in temperatures and changes to the precipitation regime.

In general, climate change will affect the distributions of species and ecosystems. It is expected that desert and sparsely vegetated habitats will spread in North America, Europe, Asia, and Southern Africa, as will grasslands in Southern Africa, Saudi Arabia, and Australia (McNeely 1995). The changes in the precipitation regime and the growing incidence of extreme events resulting from climate change will be the main reasons for forest degradation (Thauront and Stalleger 2008). Wet habitats will also be threatened by changes in precipitation, increased evaporation, and extreme weather frequency (Sefferova et al. 2008). Coastal habitats are among the most degraded. It is expected that the sea rise caused by climate change will additionally heighten the sensitivity of these habitats (Pereira et al. 2012). Mountain and alpine habitats are also one of the most vulnerable habitats to the rising temperatures caused by climate change (McNeely 1995).

Further, it is anticipated that climate change will affect various species by changing community composition and structure, shifting range, changing patterns of migration, breeding and flowering, changing morphology, and reducing genetic diversity (Sodhi et al. 2009). Many species have already altered their behavior in consequence of the ongoing climate changes (IPCC 2014).

Invasive Species

Species with narrow climate niches are the most vulnerable to climate change. However, plants with the ability to quickly adapt to changes, migrate, and inhabit new areas have a greater chance of securing their survival in the era of global changes. The latter are precisely those characteristics specific to invasive plants, which are expected to have an even greater impact on ecosystems in the future. Invasive plants are defined as naturalized plants that are capable of producing many propagules at significant distances from parent plants and consequently have the potential to spread over an extensive area (Richardson et al. 2000). In addition, species distribution models predict that the distribution of invasive species will be affected by climate change. The changes that will affect the spread of invasive plants include temperature increase, rainfall regime change, CO2 concentration increase, nitrogen deposition, and new disturbances caused by land-use change (Bradley et al. 2010).

Invasive species are considered to be one of the main factors that bear heavily on biodiversity and ecosystem functions. The introduction of new species affects the stability of an ecosystem’s key species in terms of food web and competitive relationships. Some invasive species only cause changes in communities, while others can affect the structure and functions of ecosystems and carry major implications for biodiversity and ecosystems (Maurel et al. 2010). Due to interspecific competition, invasive plants often affect each other positively or extend their influence on native species, thus impinging on a number of key processes that accelerate the replacement of native species with new, invasive ones.

Invasive species that have the potential to significantly change ecosystem processes are called ecosystem engineers. When the impact of an invasive species on nutrient cycling, transformation, and energy flow in an ecosystem is high, novel ecosystems are created (Hobbs et al. 2006). In novel ecosystems, native plants are faced with the changed habitat conditions and new competitive relationships, which cause their displacement from the habitat.

Invasive species can affect ecosystems directly and indirectly (Ehrenfeld 2010). Invasive plants have a direct effect on an ecosystem by altering the level of available resources or habitat conditions and reducing the survival rate and number of species that coexist with them. Indirect effects occur when an invasive species changes the number and activity of one or more species, thereby altering their effect on the balance of nutrients, transformation, and energy flow. It is important to point out that the impact of invasive species is context-specific and can have significantly different outcomes depending on the invasive species and habitat type in which the invasion process is present. Even a single species can produce different effects depending on different contexts, e.g., habitat exposure (Scott et al. 2001).

Many invasive species affect the habitat structure and have great potential to alter hydrological conditions. For example, Smooth cordgrass (Spartina alterniflora) forms thick monodominant stands in coastal habitats and increases sediment accumulation, alters topography, and increases the risk of floods, thus influencing bird, fish, crab, and shell populations and leading to habitat destruction (Wang et al. 2006).

Invasive plants can change the structure of vegetation and, as a result, affect the habitat and ecosystem characteristics that depend on it (Fig. 7). Invasive Amur honeysuckle (Lonicera maackii) forms a dense shrub layer in a forest which creates a homogeneous microclimate condition and lower soil surface temperature. This change in habitat conditions has a major negative impact on amphibians (Watling et al. 2011).

Fig. 7
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Changes in floristic composition caused by the highly invasive Amorpha fruticosa. Several years after the invasion, A. fruticosa forms a dense shrub layer and completely changes the vegetation structure, turning accessible areas into impassable ones. 04 June 2009. (The authors’ personal collection)

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Invasive species change the natural regime of ecosystem disturbances such as fires. As an example, annual grass invasions often change the regime of fire in natural ecosystems. Interestingly, invasive plants recover much faster after a fire than native plants, which further increases the sensitivity of a habitat to fire. Cogongrass (Imperata cylindrica) and Giant cane (Arundo donax) are aggressive, highly flammable invasive species, which are capable of changing fire frequency and intensity, as well as the size of the area affected by the fire, and of creating conditions that do not favor native species (Brooks et al. 2004).

Invasive plants can cause soil erosion. The Himalayan balsam (Impatiens glandulifera) is an annual invasive species that grows along riverbanks and produces a large number of plant residues that prevent the development of other species in the spring. Because of its shallow roots, in the autumn riverbanks are left without vegetation and are subject to erosion (Greenwood and Kuhn 2014).

Some invasive plants can influence soil properties. The most commonly cited example is the Fire tree (Morella faya), which fixes atmospheric nitrogen and increases nitrogen content in the soil, thus suppressing native species adapted to nitrogen-poor soil (Vitousek et al. 1987). The fact that many invasive plants occupy nitrogen-rich soil suggests that changes caused by the invasion of M. faya may have far greater implications for ecosystem processes than the impact on the nitrogen cycle. Another form of soil alteration is introduced by Saltcedars (Tamarix spp.), which are facultative halophytes whose leaves excrete a high concentration of salt into the soil, thereby preventing native species growth (Marlin et al. 2017).

Invasives do not just impact soil. Common waterweed (Elodea canadensis) increases the content of nutrients and organic matter in water. E. canadensis absorbs nutrients from the sediment and releases them into a waterbody, which increases the content of nutrients and causes eutrophication (Zehnsdorf et al. 2015). This further stimulates macroalgal development, which leads to even higher eutrophication levels.

Compared to native plants, the invasive ones produce large quantities of seeds; have a large specific leaf area, a different quality and quantity of residues, a more effective strategy for nutrient uptake; and change the structure and functioning of soil microbial communities (Daehler 2003). Equipped with these mechanisms, invasive species become better competitors compared to native species or change the conditions in the soil or water and thus negatively affect native species and their habitats.

Managing the Threats of Habitat Degradation

Ecosystem changes resulting from one anthropogenic disturbance are usually increased by other threats or by the synergistic effects of multiple threats. For instance, changes in habitat and ecosystem quality resulting from the influence of invasive plants are precipitated by additional factors, such as climate change, atmospheric deposition of nitrogen, acid rain, and land-use changes.

Protected Areas

One of the most effective ways to conserve species and ecosystems is to establish protected areas. Protected areas have a distinct geological, biological, ecosystem, and landscape diversity. They are defined geographically and managed in order to reach long-term nature conservation and link ecosystem services and cultural values (Dudley 2008). They offer protection of habitats from destructive human activities and play an important role in mitigating climate change because they represent major carbon sinks (Kuiters et al. 2012).

Protected areas are managed for strict protection, ecosystem conservation and protection, conservation of natural features, conservation through active management, landscape and seascape conservation and recreation, and the sustainable use of natural resources (Dudley 2008). Protected areas occupy around 12% of terrestrial ecosystems. Today’s network of protected areas includes sites with higher species richness. However, the network should be expanded, especially to the tropics, in order to include other highly endemic ecosystems (Dudley 2008).

Although establishing protected areas is the best way to protect species and ecosystems, that is not always possible. Ecosystem management includes other measures that can be taken to protect and maintain the quality of habitats, natural vegetation, and species composition.

Measures to Mitigate the Main Causes of Habitat Degradation

Agriculture is one of the main drivers of habitat loss and degradation. Accordingly, it is important to halt the conversion of natural habitats into agricultural land. Landscape components such as field margins, hedges, stone walls, small woodlands, ditches, and ground paths should be protected or restored since they present the most effective protection from soil erosion (EEA 2017). Also, they create a variety of biotopes that contribute to biodiversity and thus increase the stability and functionality of ecosystems. Further, it is necessary to adjust livestock density with the time and frequency of mowing and grazing to avoid damage to natural species and to prevent the expansion of alien invasive plants. In order to mitigate agricultural pollution, it is important to minimize the use of fertilizer and other chemicals. This measure, as well as runoff capture and filtration, could prevent fertilizer runoff and contamination of surface and underground water.

The main driver of deforestation is agriculture. Since it is estimated that agriculture needs to feed 9 billion people by 2050, it is not reasonable to expect that it will be possible to stop its expansion (Wollenberg et al. 2011). According to Angelsen (2010), agricultural policies oriented toward areas with low forest cover or toward unsustainable agricultural production systems are more reliable forest conservation strategies than those which are oriented toward agricultural stimulation of areas with a higher percentage of forest cover.

Tourism is an activity that provides an opportunity to raise funds that will be used for biodiversity management and conservation. However, tourism and recreation should be planned in accordance with accepted planning methodologies in order to reduce the impact on ecosystems and their services (CBD 2004). Establishing visitor use limits and control of the direction of tourist flow can contribute to the reduction of negative impacts.

Activities related to winter sports can have diverse impacts on soil, water, vegetation, and wildlife. In order to reduce the impacts of skiing and other winter activities, construction and usage of ski piste must be avoided if vegetation analysis reveals a presence of species whose conservation is of great importance in the targeted area (Wipf et al. 2005). Since the maintenance of ski pistes inflicts the most severe damage to the vegetation, machine-grading should be avoided, as well as snowmaking, which can cause soil and water nutrient overload.

Mining and quarrying cause land-use and land-cover changes. In addition, those activities affect biota as well as cause pollution and changes in hydrologic regimes of surface and groundwater. In order to mitigate the consequences of ecosystem degradation caused by mining and quarrying, exploitation of resources must be followed up by technical and biological recultivation.

Certainly, the production of renewable energy is more sustainable than fossil fuel production. People often assume that renewable energy production has no environmental impact, but that is not the case. There are many disturbances caused by green energy production, which impact wildlife populations, land and water use, etc. Therefore, strategic planning is a necessary tool that will enable the development of power infrastructures required to produce green energy with as little negative impact as possible to natural ecosystems (EC 2010).

Effective mitigation of climate change depends on global scale cooperation and is based on the reduction of energy use and emission of greenhouse gases (IPCC 2014). Climate change mitigation also needs to address changes in consumption patterns, the development of technologies and their transfer, and the adjustment and harmonization of legislation and government policies. Mitigating measures such as afforestation, which increases carbon sequestration, and urban planning, which seeks to reduce the use of energy and resources, can have a synergistic effect in reducing the emission of greenhouse gases and can deliver benefits to biodiversity when applied in a number of sectors.

Invasive species present a serious threat to ecosystems and human well-being. It is vital that the introduction and spread of invasive species be prevented. The introduction and spread of plants and plant pests, from one geographical area to another, are regulated by several agreements. One of the basic agreements aimed at preventing the introduction and spread of harmful plants and plant pests into new areas is the International Plant Protection Convention. The Convention defines the need for international cooperation in combating pests of plants and plant products, as well as in preventing the international spread of pests of plants and plant products, particularly their introduction into endangered areas, through the application of appropriate phytosanitary measures (FAO 1997).

Preventing the introduction of invasive species is crucial and involves a series of measures to check the intentional or unintentional introduction of invasive species to new regions. When the invasive species are introduced, detection and rapid eradication measures are taken to prevent their establishment. If invasive species are already established, it is necessary to implement measures to control the population spread. In addition, it is important to reduce ecosystem perturbations and disturbances and enhance their resilience in order to mitigate invasive species spread.

Conclusion

One of the biggest challenges facing the world is species extinction, ecosystem deterioration, and environmental degradation. All these problems are interconnected with the same drivers of change. Habitat diversity is a precondition for species diversity. However, habitats are facing tremendous pressures. Those pressures include agriculture, deforestation, urbanization, recreation, tourism, energy production, climate change, and invasive species. Agriculture is the main driver of deforestation, environmental pollution, and the overuse of natural resources. Deforestation causes radical changes in habitats, nutrient cycling, and species composition since keystone species that define the whole ecosystem are removed. Urbanization may lead to the complete destruction of ecosystems as well as numerous ecosystem disturbances which can further promote the spread of invasive species. Recreation and tourism can cause changes in species composition, chemical pollution, overuse of resources, soil degradation, noise, litter, and deforestation. Likewise, the production of energy causes habitat pollution, loss, and destruction. Further, it is predicted that climate change will negatively affect species by altering community composition and structure. Coupled with climate change, invasive plants affect the structure of vegetation and habitat, the level of available resources, and the number and activity of one or more species and thus have influences on the balance of nutrients, transformation, and energy flow.

All those pressures are directly and indirectly anthropogenically conditioned, and the economic growth of many countries has been based on activities such as agriculture, tourism, and urbanization. Although these activities are necessary and generate an economic profit, they are one of the reasons for ecosystem instability.

In order to monitor progress toward the achievement of SDGs, several indicators are proposed for each goal and its corresponding targets. Those indicators can help countries to develop implementation strategies. By tracking annual changes in forest areas and the conversion of natural ecosystems to agriculture land, areas of forest under sustainable forest management, annual changes in degraded or decertified arable land, the rate of extinction for marine and terrestrial species groups in the near future, protected areas’ overlay with biodiversity, and abundance of invasive alien species, etc., countries can measure their success toward the achievement of SDG 15 and its targets, modify or change their implementation strategies in order to successfully protect habitats, halt and reverse their degradation, and ensure their sustainable use.

Successful mitigation of biodiversity and environmental threats will depend on the measures and policies taken to meet these challenges. Since habitats are places where species live, protection, conservation, and restoration of habitats are essential to enhancing ecosystem stability, preserving ecosystem services, and managing wildlife populations. By establishing protected areas, habitat quality could be maintained or, ideally, increased. In addition, preventing the introduction of invasive species, halting the conversion of natural habitats into agricultural land, making changes in consumption patterns, developing and transferring new technologies, and implementing environmental and nature conservation policies can all help mitigate habitat pressures and reduce the effects of human activities that have detrimental environmental impacts.

Cross-References