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Around half of Earth’s terrestrial land surface remains relatively untouched by humans, a new study has found. Using a combination of recent global maps of human influence, researchers were able to calculate the average influence humans are having on ecosystems worldwide. These findings provide some hope for our ability to protect and conserve the regions of the world which, at this moment in time, remain relatively ‘wild’.

For as long as humans have existed they have impacted their surrounding environment. This era of human dominance has been coined the ‘Anthropocene Era’ by some scientists, who argue that Earth is being overwhelmingly defined by the actions of humans above natural processes. As the devastating effects of anthropogenic climate change unravel worldwide, it is hardly surprising that many people favour this view. 

Whilst it is evident that mankind profoundly impacts the natural environment, being able to quantify this is more challenging. Initial efforts to establish the global extent to which human civilisation has impacted Earth began in the 1980’s when ‘wild’ areas were identified and mapped, with efforts progressing through the following decades. 

In the study, researchers combined four different global maps of human influence to determine the average human influence for different regions in the world. Interestingly, their findings show that whilst the maps analysed use different methodologies they show similar results for the level of human influence across the globe.

They conclude that just over 50% of Earth’s land surface can be classified as having low human influence or being untouched completely, with a range of 48-56% depending on the type of human influence map used. 

Importantly, the level of human influence varies significantly from biome to biome. Cold landscapes such as boreal forests and tundra have experienced ‘very low’ to ‘low’ human influence. By comparison, temperate grasslands, tropical coniferous forests and tropical dry forests have experienced much greater levels of human influence with less than 1% of these regions being classified as having ‘very low’ human influence. For these ecosystems, it is a grim illustration that human civilisation has completely altered the natural environment.  

Ecosystems which still remain relatively untouched by humans provide a number of beneficial services to mankind such as supplying clean water and providing natural flood control as well as being able to protect against some of the impacts of climate change. One example of this is urban wetlands, which are being constructed in order to adapt to extreme weather events and flooding in urban areas, such as in Laos, by controlling water flow and filtration. These ecosystem services are also therefore crucial for improving overall human wellbeing. 

For ecosystems which have seen significant levels of human influence, all hope is not lost. Certain agricultural practices such as ‘carbon-smart’ farming, which helps to restore organic matter in the soil and increase soil-biodiversity, can actually help to promote biodiversity rather than threaten it, whilst pollinators can thrive in urban areas. Therefore, these human-dominated landscapes can actually help mitigate the climate crisis and support biodiversity if managed effectively. 

Protecting the world’s unscathed lands is beneficial for a number of reasons, the authors of the study note, as they are able to “help purify air and water, recycle nutrients, enhance soil fertility and retention, pollinate plants and break down waste products.”

Lead author of the study, Jason Riggio, who is also a postdoctoral scholar at the University of California, provides an encouraging perspective on leaving landscapes untouched, highlighting that “if we act quickly and decisively, there is a slim window in which we can still conserve roughly half of the Earth’s land surface in a relatively intact state.” 

A key aim of the study was to provide insights for the 15th Conference of the Parties to the Convention on Biological Diversity (CBD), to be able to set specific and more ambitious targets to conserve the world’s ecosystems. The meeting was due to take place in China later this year, but has been pushed back as a result of the COVID-19 pandemic and is now set to take place between the 17-30th May next year. 

Currently 20% of Earth’s terrestrial land surface is either classified as built up urban areas or cropland and with the global population expanding, this proportion will undoubtedly increase. Going forward, it is critical that we protect these ecosystems which remain relatively intact by ensuring conservation efforts are targeted and relevant. In the lead up to the CBD next year, ambitious targets are gaining momentum and the hope is that by 2050, at least half of the Earth’s surface will be conserved. 

Human civilisations can still populate a landscape and have low influence over its environment but it is a case of taking a more balanced approach towards conservation efforts. The focus needs to be on ensuring that resource needs, along with the protection of ecosystem services and biodiversity, are secured. Professor Riggio raises the point that “achieving this balance will be necessary if we hope to meet ambitious conservation targets” but highlights that “our study optimistically shows that these targets are still within reach.”

What changes has human activity caused to the Earth’s land surface? Farming is a major cause of climate change and biodiversity loss, with species abundance having fallen by over 20% globally since 1900. Diversity within agriculture fares no better, as the United Nations’ Food and Agriculture Organization (FAO) reports that just 9 species of plant account for 66% of global crop production. Meanwhile, increasing numbers of local food crops are heading towards extinction, being replaced by more marketable staples such as wheat, rice and maize. The scale of agriculture’s impact can be attributed to humanity’s influence on land surface changes: more than 70% of Earth’s land surface and two-thirds of marine environments have been significantly altered by human activity. Arable lands and grazing pastures cover one-third of Earth’s land surfaces and consume three-quarters of the world’s limited freshwater resources.

The Problems

human activity land changes
A graph showing changes to land surface through human activity by sector (Source: OurWorldinData.org). 

Land Changes by Human Activity

Habitat loss and fragmentation are the primary threats to 85% of the species on the IUCN’s Red List of threatened and endangered species. Agriculture is a major driver of this as large swathes of highly productive areas such as forest, meadow and wetland habitats are cleared to make way for fields and grazing land. The homogeneity of agricultural ecosystems (i.e. low variety of plant species and supported wildlife) caused by crop monocultures encourages low genetic biodiversity, dominance of pest species and a greater susceptibility of crops to disease. In places such as the USA, 75% of processed foods in supermarkets contain genetically modified ingredients, including 92% of maize and 94% of soybean products. These crops are cloned, such that a single disease or pest could wipe out the entire field. The resulting fragile agroecosystem fuels a reliance on pesticides, herbicides and fertilisers to promote crop growth and prevent damage.

Soil Erosion

More than 68 billion tonnes of top-soil is eroded every year at a rate 100 times faster than it can naturally be replenished. Laden with biocides and fertiliser, the soil ends up in waterways where it contaminates drinking water and protected areas downstream. Water treatment and healthcare-associated costs alone cost US taxpayers billions a year. Furthermore, exposed and lifeless soil is more vulnerable to wind and water erosion due to lack of root and mycelium systems that hold it together. Healthy soil is rich in humus, which holds more water, and decreases erosion through increased soil density and particle clumping. A key contributor to soil erosion is over-tilling: although it increases productivity in the short-term by mixing in surface nutrients (e.g. fertiliser), tilling is physically destructive to the soil’s structure and in the long-term leads to soil compaction, loss of fertility and surface crust formation that worsens topsoil erosion.   

Toxic Chemicals

Biocides are becoming less effective as pests develop resistance, prompting the development of increasingly deadly formulae. As policymakers ban a growing number of chemicals due to their detrimental effects on health, agriculture will need to turn to natural pest management alternatives. Biocides rarely distinguish between target species and beneficial invertebrates such as earthworms. Important ecosystem engineers that physically alter and regulate their environment, earthworms are vulnerable to pesticides through direct contact or ingestion, with even sublethal doses causing impairment or altered activity. They are also highly sensitive to soil pH which is lowered by the topical application of nitrogen-rich fertiliser.

Eutrophication

Conventional farming not only affects the land it occupies, but its effects are carried by the wind as aerosol particles, and by water runoff into oceans and reservoirs. The fumes from fertilizers and vehicle exhausts combine in the atmosphere to create toxic compounds, leading to respiratory issues in humans and animals, as well as dissolving into acid rain which damages forests and agricultural land, and pollutes waterways. Furthermore, excess nitrogen fertiliser cannot be taken up by the soil and runs off into bodies of water causing eutrophication and hypoxia. Eutrophication refers to the over-enrichment of water with nutrients that leads to massive algal blooms, blocking out sunlight and depleting the dissolved oxygen. This leads to low oxygen levels known as hypoxia, resulting in mass die-offs or migration of species from the affected area creating an oceanic desert. The Gulf of Mexico’s annual summer “dead zone”, which becomes so polluted that no marine life can thrive, is an extreme example of the consequences of fertiliser overuse. The Mississippi River runs through 31 U.S. states with high agricultural and industrial activity before emptying into the Gulf. This year the dead-zone is forecasted to reach 10 700 sq km, about 2 000 sq km larger than the long-term average. This trend is especially worrying because coastal waters are some of the most productive in the ocean, supporting coral reefs as well as economically important fishing and leisure industries.

The Solutions

You might also like: The Amazon is at Risk of Drying Out

human activity land changes
John Pickett et al. Push–pull farming systems, Current Opinion in Biotechnology, (2014).

Reintegrating Nature into the Countryside

There are already many solutions to these environmental issues, yet they are not being implemented on the scale that is required to halt biodiversity loss. A simple way of reintegrating nature into arable land is the creation of wild zones and hedgerows on the margins of fields, or other unused spaces. Not only would these small pockets of unmanaged land provide valuable habitats for native plants and animals, they would reconnect fragmented habitats, allowing larger ranges for populations and promoting genetic diversity. These wildlife corridors are particularly important for non-flying migratory species, and to help mitigate local extinctions as habitat ranges shift towards higher latitudes as a result of the climate crisis.

No-Till and Cover Cropping

No-till or reduced-till farming is a re-emerging technique that seeks to minimise soil disturbance and promote healthy soil ecosystems. No-till often includes planting perennial plants that retain their roots for more than one growing season. Perennials have stronger and deeper roots than annual crops, reducing soil compaction and improving aeration. These roots also provide a steady supply of soil nutrients in the form of liquid exudates to support a healthy community of microbes and macro-organisms. No-till is often combined with cover cropping to protect against erosion and improve soil health. The cover crop’s roots bind the soil in place and offer physical protection from wind and water erosion, while adding plant diversity in monoculture cropland. Some cover crops also create habitats for natural pollinators, whose presence increases crop yield and shortens the growing season. The most popular types of cover crops are grasses and legumes that scavenge nitrogen and carbon from the soil as well as sequester it from the atmosphere, add fertile humus to the soil as they break down, and provide weed control. 

Biocontrol

Biological pest control and biopesticides are two natural alternatives to conventional biocides that can also be used in conjunction with cover crops. In natural systems, pests rarely cause problems because the complex web of predator-prey interactions, competition and genetic diversity keeps the ecosystem in balance. Recreating these relationships through either the introduction or augmentation of existing predator or parasite populations is a form of biocontrol that protects crops while reducing the need for synthetic pesticides. Another technique, known as “Push-Pull”, involves planting repellent plants between crop rows to discourage pest colonisation, while establishing “pull” plants that are more attractive to the pest than the crop around the perimeter of the field. This draws pests away from the centre of the field and towards margins where predator populations are more strongly established. As a natural alternative to pesticides, biopesticides work in a multitude of ways, some imitating biochemical signals, while others introduce fungal, viral or bacterial diseases that infect the pest.

Natural fertilisers

Green manure, or mulch, is dead plant matter that is spread over a field and left to decompose. Legumes, such as vetch and clover, make especially great manure as they store carbon and nitrogen in their roots as they grow, creating high quality natural fertiliser. Unlike conventional nitrogen fertilisers that saturate the soil to achieve maximal yield, green manure releases nitrogen into the soil gradually thus preventing run-off, with major beneficial consequences for water quality. Green manure often comes from cover crops that are planted in the field and then either cut or left to wilt in place. They provide ground cover while alive, and return nutrients upon decomposition, mimicking naturally-evolved ecosystems. 

Just like in nature, the effects of individual sustainable practices overlap and integrate with each other to forge a cohesive whole. The tools and strategies for building healthy agricultural systems able to feed over 8 billion humans while preserving the environment already exist; it is simply a case of rediscovering what past agriculturalists and indigenous peoples already knew: that nature will provide on condition we work with it, not against it, and that we give back as much as we take. Moreover, investing in the study of ecosystem interactions will lead to healthier, more productive soils and a decreased reliance on toxic fertilisers and biocides. This will have overwhelmingly positive consequences for global food security, nutrition and health, as well as for the reduction of environmental damage and pollution.

China and India, the two most populous countries in the world, are making our planet greener through land management, a recent study by NASA reveals. With their aggressive afforestation and agricultural expansion, both countries lead the world in ‘greening’– a term used by climate scientists to describe Earth’s increasing vegetation cover in recent decades.

The two countries have created one-third of the word’s new forests, croplands, and other forms of vegetation in the last two decades, the study published in Nature Sustainability revealed. China, which has 6.3% of the globe’s landmass, alone accounts for 25% of the global net increase in new vegetation.

The data collected by the researchers using Moderate Resolution Imaging Spectroradiometer (MODIS)– a NASA satellite imaging sensor- shows that 42% of the greening in China comes from afforestation while 32% comes from newly cultivated farmlands. In India, 82% of the greening comes from new croplands and 4.4% from new forests.

The research also revealed that besides land management strategies adopted by China and India, indirect factors like climate change, CO2 fertilization, nitrogen deposition, and recovery from natural disturbances also lead to the greening. However, they could be a less prominent driver of global greening as compared to human-driven land use.

Green represents regions of net greening and yellow, red and purple showing regions with net browning. White areas depict barren land, permafrost, ice, wetlands, and built-up areas.

The Greening

A group of 15 scientists from various universities of China, France, Germany, the US, and India collected satellite data from MODIS, which mapped Earth’s surface from 2000 to 2017 onboard NASA’s Terra and Aqua satellites. Their analysis revealed the exponential growth of vegetation in China and India.

China’s massive-scale tree plantations on the low-productive regions of the country lead to a 16% global net greening. In just a single decade–2000-2010, the country increased its total forest area by 19% covering 434,000 Sqkm of land.

China achieved this remarkable feat by implementing a series of programmes to conserve forests, mitigate soil erosion, air pollution, and climate change.  Since the 1990s, China has invested more than $100bn in afforestation programmes and, according to its government, planted more than 35bn trees across 12 Chinese provinces. China’s forestry expenditure per hectare is over three times higher than the global average and has long exceeded that of the US and Europe.

The rapid agricultural growth in China with the help of hybrid cultivars, multiple cropping, irrigation, fertiliser use, pest control, better quality seeds, farm mechanisation, credit availability, and crop insurance programmes also paved the way for a greener nation.

The study concludes that China’s man-made vegetation in the last two decades is equal to that of the greening of Russia, the US and Canada combined.

“China engineered ambitious programmes,” the author says, “to conserve and expand forests with the goal of mitigating land degradation, air pollution, and climate change.”

Greening from forest expansion in China in two decades

The research revealed that India accounts for 6.8% of the global net increase in vegetation cover, with the new croplands contributing the most. This is roughly equal to that in the US or Canada – which both had three times more vegetated areas in 2000.

India’s green revolution which brought massive changes in agricultural production is attributed to a rapidly grown harvesting area throughout the country.

Human Land Use

The data analysis has revealed that the role of human land use in increasing vegetation on a global scale is much more important than previously understood.

Downplaying the contribution of human land use, climate scientists had previously argued that greening was a result of increased CO2 concentration in the atmosphere. But a key finding of the research paper debunks the argument and states “human land use” has been “a dominant driver” of global greening since 2000l.  The greening on Earth in recent decades has had more to do with direct human interference than the indirect effect of climate change or the CO2 fertilisation effect.

Six out of seven “greening clusters” found by the research team “overlap” with regions known to have highly intensive agriculture and human-land use. But regions like Amazone, where human land use is notably low, the rate of greening is much lower.

A group of researchers from the Centre for Conservation and Research in Sri Lanka, have suggested the construction of electric fences around human villages to save the lives of humans and elephants in the country.

Analysing the first country-wide survey on the habitats of elephants and their conflicts with humans, they say this new conservation approach model of erecting electric fences would work better than confining the animals in a specific area.

Human-elephant conflicts kill more than 250 elephants and 70 humans in Sri Lanka annually. Adult male elephants entering human habitat to feed on farm crops sets up the stage for the deadly battle between two species.

The increasing fatality from these clashes sounds the death knell of the Asian elephants that are already categorised as endangered in the International Union for Conservation of Nature (IUCN) Red List.

Since the 1950s the approach to human-elephant conflict mitigation in the country has been based around confinement of elephants in protected areas. The animals are chased away into these areas using light flares, thunder crackers and sometimes even shotguns.

These attempts rarely succeed. The scarcity of resources in the protected areas due overpopulation of Elephants compels them to venture into human villages to seek food.  

The research

The researchers headed by Dr. Prithiviraj Fernando divided the country into 2,742 grid cells, each covering an area of 25 sq km. Three residents living within each grid cell were asked to report on the presence of elephants and the severity of human-elephant conflicts.

They opted for a questionnaire-based approach rather than methods based on direct sightings. Elephants, despite their large size, are difficult to be tracked in the wild. Asian elephants tend to reside in low visibility habitats like scrub and secondary forests. They only venture out to the open during the night. They also occupy a large home range of hundreds of sq km frequently crisscrossing long distances at a stretch.

The result of the collected data was later visualised into an elephant distribution map with highlights of key areas for intervention.

You might also like: Using Abandoned Agricultural Land to Help Save The Planet

(a) Elephant presence, by herds and males; cells without resident people are coloured green. (b) Elephant presence and absence overlaid with the GPS locations of 54 elephants tracked during 2004–2018. (c) Spatio-temporal patterns of cell use by elephant herds and males (Fig. 2). (d) Severity of human–elephant conflict.

The result showed that Asian elephants inhabit 60% of Sri Lanka’s land, and more than half of their habitat coincides with human habitats. The majority, over 56% of residents, who reported the presence of elephants, had experienced major human-elephant conflicts. 23% of people faced moderate conflicts. Only 7% of residents reported having not experienced any conflicts. The study also revealed that the elephants have lost 16% of their range since 1960.

The researchers recommend a human-elephant coexistence model that promotes stakeholder awareness and mitigates conflict by protecting villages with barriers like electric fences. They say the distribution map they prepared can serve as a template for identifying areas where conflict mitigation needs to be integrated.

“If this approach is incorporated into the National Policy for Elephant Conservation and Management in Sri Lanka, it would facilitate human-elephant co-existence.” says the lead researcher Dr. Fernando. “It would also result in the reduction of human-elephant conflict.”

 

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