Soil And Land Pollution: A Threat To Animal Life

Soil and land pollution is a pressing issue that poses significant risks to both human and animal life. The presence of toxic chemicals, heavy metals, and other contaminants in the soil can have far-reaching consequences for the animals that inhabit these ecosystems. From insects and worms to birds and mammals, all forms of wildlife are vulnerable to the harmful effects of pollution. The impact of soil and land pollution on animals is a critical aspect that requires our attention to ensure the preservation of biodiversity and the overall health of our planet.

Heavy metals, fertilisers and pesticides

Heavy Metals

Heavy metals are naturally occurring components found in the earth's crust. Their presence is considered unique because their complete removal from the environment is difficult once they enter it. Heavy metals are considered one of the most critical toxicants among the multilayered soil and environmental pollutants. The existence of heavy metals in the ecosystem increases the potential intake of such toxic components by the living organisms and their accumulation in many body organs, including the kidney, liver, and bone. Moreover, the accumulation of these metals causes deleterious damage to various body systems, such as the nervous, skeletal, endocrine, immune, and circulatory systems.

Fertilisers

Fertilisers have become an indispensable part of agriculture and farming. These substances, both synthetic and organic, are added to the soil to increase the supply of essential nutrients that boost the growth of plants and vegetation. With the rapid increase in the global population, the demand for food has also been rising tremendously. Statistics show that almost 40% to 60% of agricultural crops are grown with the use of different types of fertilisers. Not only this, more than 50% of the population feeds on crops grown as a result of using synthetic fertilisers.

The use of fertilisers has helped mankind yield massive crop production to meet the food supply of the growing population. However, in order to do so, we have disregarded the adversity that lies ahead in its worst form. The cold of the winter is always counteracted by the warmth of the sun. Nature constantly works until a balance is attained, but that's just mother nature, not human nature!

We all are living with the consequences of environmental imbalance. A classic example of the same would be global warming. The reasons attributed to this global threat are nothing but the mindless actions of human civilisation—deforestation, the greenhouse effect, soil erosion, all being the results of the same. Speaking of the use of fertilisers, these chemicals and minerals undoubtedly help in boosting the growth of plants, but our environment is paying a huge price for the same, the burden of which will be shared by one and all in the long run.

The impact of fertilisers on soil quality:

Using too many fertilisers can alter the fertility of the soil by increasing the acid levels in it. The levels of soil pH vary from 0-14, wherein 0 is considered to be the most acidic and 14 is the most basic. 7 is considered to be neutral. The ideal soil pH varies from plant to plant and can be altered by bringing in some changes in the treatment of the soil. In the absence of identifying the pH levels, there are high chances that you may not be able to use that soil for plant-yielding in the long run.

In addition to altering the pH levels, synthetic fertilisers also tend to kill the beneficial microorganisms present in the soil that are essential for plant production and overall soil health. This makes agricultural growth highly dependent on fertilisers because the exposure to these substances has killed the natural ability of the soil to be potent, and without additional treatment, the soil lacks the nutrients essential for vegetation.

The impact of fertilisers on water bodies:

Excessive use of fertilisers leads to eutrophication. Fertilisers contain substances including nitrates and phosphorus that are flooded into lakes and oceans through rains and sewage. These substances boost the excessive growth of algae in the water bodies, thereby decreasing the level of oxygen for aquatic life. The deprivation leads to the death of fish and other aquatic fauna and flora. Indirectly, it contributes to an imbalance in the food chain as the different kinds of fishes in the water bodies tend to be the main food source of various birds and animals in the environment, including humans.

You would be surprised to know that almost 50% of the lakes in the United States are eutrophic! A major contributing factor for the same is the use of fertilisers in private lawns. The nitrogen present in fertilisers breaks down into nitrates and reaches the groundwater. This contaminated groundwater can reach the lakes and rivers in the nearby vicinity, and also pollute the domestic water supply.

The impact of fertilisers on global warming:

Fertilisers consist of substances and chemicals including methane, carbon dioxide, ammonia, and nitrogen, resulting in the increased quantity of greenhouse gases present in the environment. In fact, nitrous oxide, which is a byproduct of nitrogen, is the third most significant greenhouse gas after carbon dioxide and methane. It also destroys the ozone layer that protects the earth from the harmful ultraviolet rays of the sun. This, in turn, is adding furthermore to the threat of global warming and subsequent weather changes.

Most fertilisers use peat as a crucial ingredient. Peat bogs tend to store greater amounts of carbon dioxide than the tropical rainforests of the entire world. Harvesting these could worsen the concentration of carbon dioxide in the atmosphere, making matters even worse.

The impact of fertilisers on plant health:

It isn't uncommon for organic fertilisers to contain sewage sludge, yes, the very sludge that comes from the wastewater of chemical industries and includes heavy metals and various harmful substances. A February 2008 study of Environmental Science and Technology revealed that the earthworms dwelling in the soil treated with such fertilisers were absorbing these harmful chemicals. This finding paved the way for the scientists to suspect the presence of these substances in the plants grown on these soils as well. Fertiliser usage has also been associated with the decrease in nutritional value in many foods in the past 50-60 years.

Treating the soil with too much nitrogen also leads to the loss of certain plant species, especially those with fewer nitrogen needs. It also encourages the growth of weeds and non-native plants. According to the Ecological Society of America, the non-native grasses are highly flammable and have a potential risk of catching wildfires, thereby posing a threat to the environment.

The impact of fertilisers on human health:

As mentioned earlier, the presence of nitrogen and other chemicals in fertilisers can also affect the groundwater and contaminate the water source of domestic usage! One of the most common results of drinking this polluted water is the development of Blue Baby Syndrome. As the name suggests, this syndrome affects infants and decreases the level of oxygen in their blood, causing their skin colour to change to blue-green. This condition can also lead to coma, and even death.

Other health hazards linked with the contact or consumption of fertiliser-infected air, water, or food include goitre, hypertension, respiratory ailments, heart disease, etc. Interestingly, nitrogen contamination from fertilisers has also been established as a crucial trigger for certain cancers, such as gastric cancer, testicular cancer, and stomach cancer.

The use of fertilisers for agricultural growth and cultivation is keeping our stomachs filled for now, but then, if things keep progressing in the same manner, it won't be long when all will be lost—food, water, and health. The irony of it all is that as harmful as the use of fertilisers is, we have come to a point where we cannot afford to not use them at all. This is because the lack of these would not only lead to less crop production but also lead to soil erosion due to lesser plant growth. The only option we have is to use organic fertilisers in moderation and take necessary steps to allow the soil to replenish its lost nutrients naturally.

Pesticides

Pesticides are toxic substances or a mixture of substances that are naturally or chemically synthesised. These are widely used for controlling harmful weeds (herbicides), fungi (fungicides), bacteria (bactericides), and insect infestations (insecticides) in the agricultural field. Moreover, these can be used against some disease carriers and pests (e.g., ticks, rodents, mosquitoes, and lice) in the entire ecosystem. Agricultural fields are the largest consumer, which represent about 85% of the global production of pesticides. Furthermore, these can help suppress and prevent insect infestation outbreaks, fungi, and bacteria in moisturised areas (carpets, refrigerators, and cupboards, etc.).

The excessive and uncontrolled use of pesticides on different crop species leads to harmful effects on beneficial biota, including honey bees, predators, birds, plants, small mammals, and humans. In addition, these ramifications create an imbalance in the biodiversity of the entire ecological system. Many systemic pesticides, their derivatives, and metabolites are investigated to be moderately safe to beneficial biota, especially beneficial insects, after their direct contact with such toxicants when they feed on plant tissues. As systemic pesticides can contaminate the floral and extrafloral nectar parts when transmitted systemically through the plant's vascular system, it leads to high percentages of mortality to honeybees and nectar-feeding parasitoids.

Moreover, many pesticides, such as chlordane, dieldrin, hexachlorobenzene thiobencarb, and endrin, resist degradation (persistent organic pollutants) and remain in the environment for a long time. Furthermore, persistent pesticide residues can be bio-accumulated and reach up to a bio-concentration more than 70,000-fold compared with the original concentration. A study done by Ligor et al. investigated the residues of five neonicotinoids (thiamethoxam, imidacloprid, acetamiprid, clothianidin, and thiacloprid) that were detected in different honey samples collected from different countries. The concentrations of residues depended on the used amount of pesticides (excessive or moderate use), which reflect the accumulation and the toxic effects of such residues on pollinators (honeybees) and other beneficial organisms.

The mechanistic pathway of pesticides starting from the time of application followed by photodegradation, absorption by the plant parts (stem, leaves, or fruit), or sorption at the soil level. Once the pesticides reach the soil, they undergo several biodegradation processes; chemical decomposition (pH, humidity, and temperature) and biological degradation (microorganisms' enzymes). The pesticides residues and degradation by-products uptake through roots via xylem to the entire plant parts causing some deleterious effects to soil and plant. These effects include overproduction of ROS, oxidative stress, DNA damage, photosynthetic blockage, necrosis, chlorosis, leaves twisting, and ultimately ended with plant death.

The effect of pesticides toxicity on agricultural soil:

Many pesticides are being used extensively in the agricultural field to prevent pest damage and improve crop production without considering their harmful effects. As a result of that uncontrolled use, pesticide residues significantly congregate in the soil and increase the contamination, which is directly or indirectly harmful to fauna and flora. On the soil level, pesticides can alter the physico-chemical and biological properties of the soil. They can also ultimately disturb microbial activity. Filimon et al. studied the negative impacts of two insecticides (Cypermethrin and Thiomethoxam) on the soil to test a range of physical parameters and determine some biochemical and microbial activities. The results showed that Thiomethoxam leads to a decrease in phosphatase activity by 6.5% compared with the control. The number of nitrifying bacteria significantly decreased to 58.1%. Physico-chemical properties were positively correlated with phosphatase, urease, and dehydrogenase activities, while negatively correlated with the aerobic nitrogen-fixing bacteria (Azothobacter vinellandi) and nitrifying bacteria. Moreover, Cypermethrin leads to a decrease in the activity of the dehydrogenase enzyme by 32.8%. Likewise, the number of nitrifying bacteria decreased by 74%. In addition, humidity and pH values were directly proportioned with urease and dehydrogenase activities and the number of nitrifying bacteria as (r > + 0.9) and (r > + 0.8), respectively.

Recently, Al-Ani et al. determined the influence of two insecticides, Miraj (Alphacypermethrin 10%) and Malathion (50% WP), on soil microorganisms (actinomycetes, fungi, and bacteria) and CO2 production. The results revealed that CO2 production decreased significantly for both insecticides. At week seven, the CO2 production values were 32% and 36% for Miraj insecticide concentrations of 100 and 200 ppm, respectively. While for Malathion application with 50, 100, and 200 ppm, the CO2 production values decreased by 42, 45, and 52%, respectively. Moreover, the number of microorganisms and the microbial activity were inversely proportional to the insecticide's concentrations added to the soil samples. These results agree with Yousaf et al., who presented the poisonous nature of insecticides to soil microorganisms due to the reduction in the production rate of CO2. Goswami et al. showed similar data that applying high concentrations of Cypermethrin insecticide leads to a severe impact on soil respiration and biomass. The effect of organophosphorus insecticides (dimethoate, diazinon, and Malathion) on soil's microbial communities during 24, 48, and 72 h. The results reflected that microbial growth was significantly inhibited according to the concentration and the exposure time. The repeated application of chlorpyrifos, Malathion, lindane, and endosulfan insecticides reduced the nitrification and denitrification processes in the soil even when these insecticides are applied at the field-recommended doses. Many earlier studies focus on the hazardous effects of different insecticides on various plant species and agricultural soils. Carbamate pesticides inhibit the activity of the nitrogenase enzyme of Azospirillum sp. Furthermore, they suppress the growth of various types of soil fauna. Niewiadomska stated that imazetapir, carbendazim, and thiram pesticides reduced nitrogenase activity in some plant species, including Rhizobium trifolii, R. leguminosarum, and Sinorhizobium melilot in cultivated samples and under field conditions. Quinalphos decreases soil nitrification and ammonification processes.

The application of herbicides, especially glyphosate-based herbicides, causes various risks on microbial fauna depending on the application period. Some indirect risks to biodiversity occurred due to the alternation in the physiological and biosynthetic mechanisms of soil ecosystems. Some combinations of herbicides with heavy metals and inorganic fertilisers inhibit the functions of microbial soil communities. Such communities are highly intolerant of herbicides' synergistic interaction with other compounds than the application of a single herbicide. For example, Arif et al. reported that Bromoxynil and Methomyl herbicides decrease the oxidation reaction of methane (CH4) to CO2. 2,4-D decreases the activity of nitrogenase, phosphatase enzymes, and hydrogen photoproduction of purple non-sulfur bacteria and harm the activities of Rhizobium sp. Moreover, Glyphosate leads to a reduction in phosphatase enzyme activity and the growth activity of azotobacter.

Fungicides are classified as the third most broadly used pesticide group after insecticides and herbicides that are being used effectively nowadays for crop protection. Furthermore, they cause harmful effects on non-target organisms such as soil microbial communities and influence soil biochemical processes like respiration. Baćmaga et al. investigated that the urease enzyme was the most sensitive to the excessive exposure of azoxystrobin. Baćmaga et al. reported that Falcon 460 EC fungicide significantly suppresses the activity of alkaline phosphatase, acid phosphatase, catalase, urease, and dehydrogenase enzymes in soil samples. In addition, overexposure to these active ingredients causes harmful effects on soil-dwelling microbial communities. Fungicides can neutralise soil enzyme activity due to the alleviation of some substances, such as compost and manure. Saha et al. reported that tebuconazole has short-term hazardous effects on soil enzymatic activities (arylsulfatase, phosphatase, urease, and fluorescein). Baćmaga et al. stated that the Chlorothalonil affected the soil microbial communities and the biochemical properties. Moreover, they lead to the stimulation of heterotrophic and actinobacteria. The hazardous effects of Chlorothalonil were observed with applications higher than the recommended doses.

The effect of pesticides toxicity on plants:

Plant transpiration facilitates the absorption of pesticides, which are soluble in soil, into all parts of the plant. Pesticides translocation occurs through the root system, followed by the vascular system. The presence of their metabolites in the plant vascular system is determined by factors like their reactions with soil and plant, doses of the applied pesticide, biochemical and physicochemical properties of the pesticide, and the mechanism of pesticide entry. The deleterious effects of pesticides on plants can be detected as chlorosis, burns, leaves twisting, stunting, and necrosis. The exposure to organophosphorus insecticide chlorpyrifos suppressed the nitrogen metabolism and growth of Vigna radiata L. (mung bean). Parween et al. investigated chlorpyrifos insecticide's metabolism and the response of the anti-oxidative enzymatic system of Vigna radiata L. during the different stages of growth after the application. The results showed that chlorpyrifos increased the rate of lipid peroxidation and proline content at a concentration of 1.5 mM during the post-flowering time. Moreover, ascorbate and glutathione levels significantly declined during all developmental stages. The activity of antioxidant enzymes increased with all concentrations during the pre-flowering stage. Sharma et al. found that Imidacloprid insecticide caused a reduction in the levels of many phytochemical substances in Brassica juncea, mustard plant.

Spraying herbicides around the vegetative parts of plants negatively affects the flowering and seed production of plants. Such changes cause pigment discoloration and affect the antioxidant enzymes involved in the defence system, lipid peroxidation, and endogenous hormone levels of non-target plants. Kaya and Doganlar reported that the application of imazapic herbicide induces some phytotoxic effects for tobacco plants, including carotenoids, jasmonic acid, antioxidant enzyme activity, and malondialdehyde contents. Recently, Fernandes et al. investigated the effect of glyphosate-based herbicides (GBH) on a non-target plant (Medicago sativa L.). The results reflected an increase in lipid peroxidation that leads to the suppression of roots and shoots growth. Overall, GBH-contaminated soils can greatly destroy the development of non-target plants.

The excessive use of fungicides exerts risky influences on plants (during different growth stages) that cannot be eliminated directly. The Falcon 460 EC fungicide showed adverse effects on root elongation and seed germination of some plant species, Sorgo Saccharum, Lepidium sativum, and Sinapsis alba. In addition, the most inhibitory effects were observed on S. alba. Hydrogen

Contaminated food and water

Bioaccumulation of Toxins in the Food Chain:

Soil pollution often involves the presence of toxic chemicals, such as heavy metals and persistent organic pollutants (POPs). These toxins can enter the food chain when animals consume contaminated plants or other animals. Over time, these pollutants accumulate in the tissues of animals, a process known as bioaccumulation. This is particularly harmful to top-level predators, such as eagles and bears, as the toxins become more concentrated as they move up the food chain.

Reduced Food Quality and Availability:

Soil and land pollution can directly affect the quality and availability of food sources for animals. Contaminants can reduce soil fertility, impacting the growth and nutritional content of plants. Additionally, certain pollutants can cause excessive growth of algae, creating "dead zones" where underwater plants and fish cannot survive due to a lack of oxygen. This disrupts the food chain and affects animals that rely on these sources for nourishment.

Water Contamination:

Soil pollution can lead to the poisoning of underground water tables and surface water bodies. Toxins from contaminated soil can percolate into groundwater, making it unsafe for consumption. Similarly, pollutants from agricultural runoff, industrial waste, and oil spills can contaminate lakes, rivers, and streams. These water sources are essential for animal survival, and their contamination can have far-reaching consequences for aquatic ecosystems and animals that depend on them.

Health Risks and Reproductive Issues:

Consuming contaminated food or water can expose animals to various health risks. Toxins can accumulate in animal tissues, leading to organ injury, endocrine disruption, increased vulnerability to diseases, and reproductive issues. For example, high levels of mercury can cause neurological problems in wildlife, impairing motor skills and reproductive functions. Pollutants can also affect the genetic makeup of animals, leading to congenital illnesses and chronic health issues.

Ecosystem Disruptions:

Soil and land pollution can have cascading effects on ecosystems, altering the abundance and health of dependent species. For instance, the loss of certain fish species due to water contamination can impact eagles and ospreys that rely on them for food. Changes in the availability of food sources can have ripple effects throughout the food web, affecting the dynamics of entire ecosystems.

Addressing soil and land pollution is crucial to mitigate these impacts on animals and maintain the delicate balance of our ecosystems. Preventative measures, such as reducing the use of chemical fertilizers, improving waste management practices, and promoting sustainable agricultural practices, are essential steps toward protecting animal health and ensuring the availability of uncontaminated food and water sources.

Habitat and food supply

Soil and land pollution have a detrimental effect on the habitats and food supply of animals. The contamination of soil and land can be caused by unsustainable agricultural practices, the improper disposal of waste, mining, illegal dumping, littering, and construction. These pollutants can include heavy metals, fertilisers, pesticides, plastic, litter, and pharmaceuticals.

The impact of these pollutants on animal habitats can be devastating. For example, the use of herbicides and clear-cutting to convert forests to agricultural land destroys habitats for mammals and other wildlife, leading to extinction. Soil pollution can also alter the composition and structure of the soil, affecting its ability to support plant life and filter water. This can lead to soil erosion, water contamination, and a loss of fertile land for agriculture.

Additionally, soil and land pollution can contaminate water bodies, making them too acidic for some animals to survive or disrupting their physiological functions. Acid rain, for instance, can increase the release of heavy metals such as aluminium into water habitats, proving toxic to aquatic life.

The food supply for animals is also impacted by soil and land pollution. Pollutants can enter the food chain, damaging the supply and quality of food. For example, animals may ingest chemicals used in agriculture, which are then passed along the food chain through bioaccumulation. Top-level predators such as bears and eagles are particularly susceptible to the bioaccumulation of air pollutants like heavy metals and persistent organic pollutants (POPs).

Furthermore, the improper disposal of animal waste on factory farms can lead to the release of pollutants. When liquid manure is sprayed onto fields, it can run off into surface waters, impacting local water supplies and the health of aquatic animals.

Overall, soil and land pollution have far-reaching consequences for animal habitats and food supplies, leading to habitat destruction, biodiversity loss, and potential harm to animal health.

Bioaccumulation

Causes of Bioaccumulation

Industrial Emissions

Factories and industrial processes release a range of chemicals and pollutants, including heavy metals and organic pollutants, into the environment. These substances then become available for absorption by organisms, leading to bioaccumulation.

Agricultural Runoff

The use of pesticides, herbicides, and fertilizers in agriculture can result in these chemicals leaching into nearby water bodies. This increases the concentration of such substances in aquatic ecosystems and the organisms that inhabit them, contributing to the process of bioaccumulation.

Persistence of Contaminants

The persistence of contaminants in the environment is another critical factor. Some substances, like heavy metals (mercury, lead, and cadmium) and certain synthetic chemicals (polychlorinated biphenyls, or PCBs), are highly stable and resist degradation, leading to their prolonged presence and increased potential for bioaccumulation.

Biological Factors

The biological characteristics of organisms also play a role in bioaccumulation. Organisms with slower metabolisms may accumulate substances more readily as they are unable to metabolize or excrete them at a rate that prevents buildup. Carnivorous species at the top of the food chain are particularly susceptible, as they consume contaminated prey, leading to higher concentrations of toxins in their bodies.

Effects of Bioaccumulation

Ecological Disruption

Human Health Risks

Threats to Endangered Species

Endangered species are already vulnerable, and bioaccumulation further exacerbates their risk of extinction. The accumulation of contaminants can push these species closer to extinction by compromising their reproductive abilities and overall health.

Environmental Persistence

Some contaminants that bioaccumulate are highly persistent in the environment. Even after the source of contamination is removed, the effects can linger, continuing to harm ecosystems and organisms. This makes it challenging to mitigate the impacts of bioaccumulation fully.

Solutions to Bioaccumulation

Regulation and Legislation

Government regulations and legislation are crucial in combating bioaccumulation. These measures can restrict the release of contaminants and enforce stricter controls on industries that produce or use bioaccumulative substances.

Sustainable Agriculture

Adopting sustainable agricultural practices, such as organic farming, crop rotation, and integrated pest management, can minimize the use of pesticides and fertilizers, reducing soil and water contamination.

Efficient Waste Management

Proper waste management and disposal are essential for preventing contaminants from entering the environment. Recycling, safe disposal of hazardous materials, and the treatment of industrial effluents can significantly reduce the release of bioaccumulative substances.

Conservation and Habitat Restoration

Conservation efforts focused on protecting and rehabilitating ecosystems can help mitigate the impacts of bioaccumulation. Restoring natural habitats and preserving biodiversity creates more resilient ecosystems better equipped to handle contaminants.

Climate change

Impact on Habitats:

Soil and land pollution can degrade and alter natural habitats, making them unsuitable for many animal species. For example, pollution can lead to soil erosion, loss of fertile land, and habitat destruction. This, in turn, can force animals to flee their natural habitats or face endangerment and extinction.

Changes in Seasonal Patterns:

Water Availability:

Soil pollution can impact water availability and quality for animals. Contaminants from soil pollution, such as heavy metals and toxic substances, can leach into water sources, making them unsafe or unsuitable for certain species. This can lead to a decline in aquatic animal populations and disrupt the food chain.

Food Supply and Quality:

Land and soil pollution can affect the availability and quality of food sources for animals. Pollutants can enter the food chain, leading to bioaccumulation of toxic substances in animal tissues. This can result in health issues, reduced reproductive success, and even death among animals, particularly top-level predators.

Vulnerabilities to Pollution:

Different animals have unique vulnerabilities to soil and land pollution. Their exposure and susceptibility to pollutants depend on their interaction with the environment and their physiological characteristics, such as their respiratory or gas exchange systems. For example, air pollution can harm the lungs and cardiovascular systems of animals, similar to its effects on humans.

Loss of Biodiversity:

Soil and land pollution contribute to biodiversity loss, which has far-reaching consequences for animal species. The destruction of habitats and the alteration of ecosystems can lead to the extinction of plant and animal species, disrupting the delicate balance of nature and impacting the survival of other species within the ecosystem.

Addressing soil and land pollution is crucial for mitigating climate change and protecting animal life. Implementing sustainable agricultural practices, reducing greenhouse gas emissions, and preserving healthy soils are essential steps toward minimizing the impact of climate change on animals and ensuring their long-term survival.

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