Soil health

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Soil health is a state of a soil meeting its range of ecosystem functions as appropriate to its environment. In more colloquial terms, the health of soil arises from favorable interactions of all soil components (living and non-living) that belong together, as in microbiota, plants and animals. It is possible that a soil can be healthy in terms of ecosystem functioning but not necessarily serve crop production or human nutrition directly, hence the scientific debate on terms and measurements.

Contents

Soil health testing is pursued as an assessment of this status [1] but tends to be confined largely to agronomic objectives. Soil health depends on soil biodiversity (with a robust soil biota), and it can be improved via soil management, especially by care to keep protective living covers on the soil and by natural (carbon-containing) soil amendments. Inorganic fertilizers do not necessarily damage soil health if they are not used in excess, and if they bring about a general improvement of overall plant growth which contributes more carbon-containing residues to the soil.

Aspects

The term soil health is used to describe the state of a soil in:

The phrase "soil health" has largely replaced the older "soil quality". The primary difference between the two expressions is that soil quality was focused on individual traits within a functional group, as in "quality of soil for maize production" or "quality of soil for roadbed preparation" and so on. The addition of the word "health" shifted the perception to be integrative, holistic and systematic. The two expressions still overlap considerably. Soil health as an expression derives from organic or "biological farming" movements in Europe, however, well before soil quality was first applied as a discipline around 1990. In 1978, Swiss soil biologist Dr Otto Buess wrote an essay "The Health of Soil and Plants" which largely defines the field even today.

The underlying principle in the use of the term "soil health" is that soil is not just an inert, lifeless growing medium, which modern intensive farming tends to represent, rather it is a living, dynamic and ever-so-subtly changing whole environment. It turns out that soils highly fertile from the point of view of crop productivity are also lively from a biological point of view. It is now commonly recognized that soil microbial biomass is large: in temperate grassland soil the bacterial and fungal biomass have been documented to be 1–2 t (2.0 long tons; 2.2 short tons)/hectare and 2–5 t (4.9 long tons; 5.5 short tons)/ha, respectively. [4] Some microbiologists now believe that 80% of soil nutrient functions are essentially controlled by microbes. [5] [6]

Using the human health analogy, a healthy soil can be categorized as one:

Conceptualisation

SoilHealthConcept.jpg

Soil health is the condition of the soil in a defined space and at a defined scale relative to a set of benchmarks that encompass healthy functioning. It would not be appropriate to refer to soil health for soil-roadbed preparation, as in the analogy of soil quality in a functional class. The definition of soil health may vary between users of the term as alternative users may place differing priorities upon the multiple functions of a soil. Therefore, the term soil health can only be understood within the context of the user of the term, and their aspirations of a soil, as well as by the boundary definition of the soil at issue. Finally, intrinsic to the discussion on soil health are many potentially conflicting interpretations, especially ecological landscape assessment vs agronomic objectives, each claiming to have soil health criteria.

Interpretation

Different soils will have different benchmarks of health depending on the "inherited" qualities, and on the geographic circumstance of the soil. The generic aspects defining a healthy soil can be considered as follows:

This translates to:

An unhealthy soil thus is the simple converse of the above.

Measurement

On the basis of the above, soil health will be measured in terms of individual ecosystem services provided relative to the benchmark. Specific benchmarks used to evaluate soil health include CO2 release, humus levels, microbial activity, and available calcium. [7]

Soil health testing is spreading in the United States, Australia and South Africa. [8] Cornell University, a land-grant college in NY State, has had a Soil Health Test since 2006. Woods End Laboratories, a private soil lab founded in Maine in 1975, has offered a soil quality package since 1985. Both these services combine physical (aggregate stability), chemical (mineral balance), and biological (CO2 respiration) analyses, which today are considered hallmarks of soil health testing. [9] The approach of other soil labs also entering the soil health field is to add into common chemical nutrient testing a biological set of factors not normally included in routine soil testing. The best example is adding biological soil respiration ("CO2-Burst") as a test procedure; this has already been adapted to modern commercial labs in the period since 2006.

There is however resistance among soil testing labs and university scientists to add new biological tests, primarily because the established metric of soil fertility is largely based on models constructed from "crop response" studies, which match crop yield to specific chemical nutrient concentrations, and no similar models appear to exist for soil health tests. Critics of novel soil health tests argue that they may be insensitive to management changes. [10]

Soil test methods have evolved slowly over the past 40 years. However, in this same time USA soils have also lost up to 75% of their carbon (humus), causing biological fertility and ecosystem functioning to decline; how much is debatable. Many critics of the conventional system say the loss of soil quality is sufficient evidence that the old soil testing models have failed us, and need to be replaced with new approaches. These older models have stressed "maximum yield" and " yield calibration" to such an extent that related factors have been overlooked. Thus, surface and groundwater pollution with excess nutrients (nitrates and phosphates) has grown enormously, and early 2000s measures were reported (in the United States) to be the worst it has been since the 1970s, before the advent of environmental consciousness. [11] [12] [13]

Regenerative Agriculture & Soil Health

Regenerative agriculture (RA) is a holistic approach to farming that emphasizes soil conservation, biodiversity, and sustainable land management. Utilizing various soil health practices, regenerative agriculture "integrates local and indigenous knowledge of landscapes, as well as their management, with established scientific knowledge" [14] while aiming to improve the socioeconomic well-being of a community [15] . Central to RA is the principle that healthy soil is foundational to sustainable agriculture, essentially focusing on feeding the soil rather than feeding each plant. RA serves as an opportunity to directly apply soil health practices to produce crops sustainably. Research highlights that regenerative agriculture enhances nutrient cycling while supporting biodiversity and ecosystem services, which are vital for maintaining soil health [16] [14] . Practices such as cover cropping, crop rotation, no-till farming, integrated pest management, permaculture, and composting support self-sustaining soil ecosystems – further enriching soil fertility while reducing dependence on chemical fertilizers and pesticides, demonstrating that cover crops not only reduce erosion but also improve nutrient cycling [15] [17] .

RA's primary contributions to soil health is the enhancement of organic matter and microbial activity. A myriad of practices can be used to increase soil organic content, like cover cropping, composting, and crop rotation to improve soil fertility, water retention, and ability to resist soil erosion. Research supports that soil microbial diversity is critical for maintaining fertility and resilience against the changing climate, and regenerative practices have been shown to enhance and support this biodiversity [17] . Cover crops act as a protective blanket during the winter months, preventing compaction and erosion, while their roots maintain soil structure and nurture microbial diversity. Crop rotation further enriches soil microbiomes by diversifying nutrient and microbial inputs, disrupting pest cycles, and decreasing reliance on chemical inputs [14] . Similarly, no-till farming minimizes physical disturbances to the soil, preserving its structure and improving water infiltration while conserving organic matter and keeping carbon in the soil, and not in the atmosphere. [18] [15] [19] . Permaculture is a design philosophy often incorporated into RA due to its focus on sustainable, ecosystem-based farming practices. Permaculture supports soil health by fostering natural nutrient cycles through techniques like companion planting, mulching, and perennial cropping. It emphasizes the creation of agricultural systems that model and mimic natural ecosystems, promoting biodiversity, more efficient resource use, and long-term soil health. These practices minimize soil erosion, enhance organic matter, and encourage beneficial microbial activity [20] .

Regenerative agriculture offers significant economic and community benefits as well, nurturing resilient farming systems that enhance local economies and promote social well-being. Economically, RA reduces input costs by minimizing reliance on chemical fertilizers and pesticides, leading to lower operational expenses and increased profitability for farmers [18] . Enhanced soil health from practices such as cover cropping and composting improves crop yields and market quality, which can provide greater productivity and financial stability. Although, the lack of heavy machinery increases the amount of necessary labor and steepens dependence on workers [15] . Additionally, RA is designed to support community health by improving access to fresh local produce and working to alleviate food insecurity. Through RA, Community Supported Agriculture (CSA) systems can be established to bridge the divides between farmers and consumers, strengthen community ties, and facilitate a direct-market relationship. These practices not only sustain farmers but benefit surrounding communities by promoting sustainable livelihoods and resilience to environmental changes [21] [17] .

RA also addresses climate challenges by promoting carbon sequestration through practices like composting and no-till farming. These methods not only mitigate climate change by lowering atmospheric CO2 levels but also improve soil health, boosting soil productivity and resilience [22] (Mishra et al. 295-309). Increasing soil organic carbon through RA practices has measurable effects on reducing atmospheric CO2 levels while improving soil functionality [21] [23] . The addition of organic material increases levels of soil organic carbon, thereby reducing atmospheric CO2 levels and enhancing soil fertility and productivity [24] .

These practices collectively cultivate a resilient soil ecosystem that supports plant growth, enhances pest and disease resistance, and mitigates greenhouse gas emissions through carbon storage. However, despite its many benefits, RA faces challenges in assessment and widespread adoption. Biological indicators of soil health are often underrepresented in current evaluations due to their complexity and the context-specific knowledge required, as biological indicators of soil health often require context-specific ecological knowledge and are not universally standardized [16] [17] . Addressing these gaps and advancing research into RA’s ecological and socioeconomic impacts will be crucial for its broader implementation and success.

Soil health gap

Fig. Concept of Soil Health Gap 1-s2.0-S2351989420305680-gr1 lrg.jpg
Fig. Concept of Soil Health Gap

The importance of soil for global food security, agro-ecosystem, environment, and human life has exponentially shifted the research trends toward soil health. However, the lack of a site/region-specific benchmark has limited the research toward understanding the effect of different agronomic managements on soil health. In 2020, Maharjan and his team introduced a new term and concept, "Soil Health Gap" and described how native land in a particular region can help in establishing the benchmark to compare the efficacies of different management practices and at the same time, it can be used in understanding quantitative difference in soil health status. [25]

See also

Related Research Articles

<span class="mw-page-title-main">Crop rotation</span> Agricultural practice of changing crops

Crop rotation is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. This practice reduces the reliance of crops on one set of nutrients, pest and weed pressure, along with the probability of developing resistant pests and weeds.

Organic farming, also known as organic agriculture or ecological farming or biological farming, is an agricultural system that emphasizes the use of naturally occurring, non-synthetic inputs such as compost manure, green manure, and bone meal and places emphasis on techniques such as crop rotation, companion planting, and mixed cropping. Biological pest control methods such as the fostering of insect predators are also encouraged. Organic agriculture can be defined as "an integrated farming system that strives for sustainability, the enhancement of soil fertility and biological diversity while, with rare exceptions, prohibiting synthetic pesticides, antibiotics, synthetic fertilizers, genetically modified organisms, and growth hormones". It originated early in the 20th century in reaction to rapidly changing farming practices. Certified organic agriculture today accounts for 70 million hectares globally, with over half of that total in Australia.

<span class="mw-page-title-main">Sustainable agriculture</span> Farming approach that balances environmental, economic and social factors in the long term

Sustainable agriculture is farming in sustainable ways meeting society's present food and textile needs, without compromising the ability for current or future generations to meet their needs. It can be based on an understanding of ecosystem services. There are many methods to increase the sustainability of agriculture. When developing agriculture within sustainable food systems, it is important to develop flexible business processes and farming practices. Agriculture has an enormous environmental footprint, playing a significant role in causing climate change, water scarcity, water pollution, land degradation, deforestation and other processes; it is simultaneously causing environmental changes and being impacted by these changes. Sustainable agriculture consists of environment friendly methods of farming that allow the production of crops or livestock without causing damage to human or natural systems. It involves preventing adverse effects on soil, water, biodiversity, and surrounding or downstream resources, as well as to those working or living on the farm or in neighboring areas. Elements of sustainable agriculture can include permaculture, agroforestry, mixed farming, multiple cropping, and crop rotation.

<span class="mw-page-title-main">Topsoil</span> Top layer of soil

Topsoil is the upper layer of soil. It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs.

<span class="mw-page-title-main">Soil fertility</span> The ability of a soil to sustain agricultural plant growth

Soil fertility refers to the ability of soil to sustain agricultural plant growth, i.e. to provide plant habitat and result in sustained and consistent yields of high quality. It also refers to the soil's ability to supply plant/crop nutrients in the right quantities and qualities over a sustained period of time. A fertile soil has the following properties:

Biointensive agriculture is an organic agricultural system that focuses on achieving maximum yields from a minimum area of land, while simultaneously increasing biodiversity and sustaining the soil fertility. The goal of the method is long term sustainability on a closed system basis. It is particularly effective for backyard gardeners and smallholder farmers in developing countries, and also has been used successfully on small-scale commercial farms.

<span class="mw-page-title-main">Organic fertilizer</span> Fertilizer developed from natural processes

Organic fertilizers are fertilizers that are naturally produced. Fertilizers are materials that can be added to soil or plants, in order to provide nutrients and sustain growth. Typical organic fertilizers include all animal waste including meat processing waste, manure, slurry, and guano; plus plant based fertilizers such as compost; and biosolids. Inorganic "organic fertilizers" include minerals and ash. Organic refers to the Principles of Organic Agriculture, which determines whether a fertilizer can be used for commercial organic agriculture, not whether the fertilizer consists of organic compounds.

Agricultural soil science is a branch of soil science that deals with the study of edaphic conditions as they relate to the production of food and fiber. In this context, it is also a constituent of the field of agronomy and is thus also described as soil agronomy.

Soil biodiversity refers to the relationship of soil to biodiversity and to aspects of the soil that can be managed in relative to biodiversity. Soil biodiversity relates to some catchment management considerations.

<span class="mw-page-title-main">The Rodale Institute</span>

Rodale Institute is a non-profit organization that supports research into organic farming. It was founded in Emmaus, Pennsylvania, in 1947 by J. I. Rodale, an organic living entrepreneur. After J.I. Rodale died in 1971, his son Robert Rodale purchased 333 acres and moved the farm to Kutztown, Pennsylvania.

The environmental impact of agriculture is the effect that different farming practices have on the ecosystems around them, and how those effects can be traced back to those practices. The environmental impact of agriculture varies widely based on practices employed by farmers and by the scale of practice. Farming communities that try to reduce environmental impacts through modifying their practices will adopt sustainable agriculture practices. The negative impact of agriculture is an old issue that remains a concern even as experts design innovative means to reduce destruction and enhance eco-efficiency. Animal agriculture practices tend to be more environmentally destructive than agricultural practices focused on fruits, vegetables and other biomass. The emissions of ammonia from cattle waste continue to raise concerns over environmental pollution.

<span class="mw-page-title-main">Agricultural pollution</span> Type of pollution caused by agriculture

Agricultural pollution refers to biotic and abiotic byproducts of farming practices that result in contamination or degradation of the environment and surrounding ecosystems, and/or cause injury to humans and their economic interests. The pollution may come from a variety of sources, ranging from point source water pollution to more diffuse, landscape-level causes, also known as non-point source pollution and air pollution. Once in the environment these pollutants can have both direct effects in surrounding ecosystems, i.e. killing local wildlife or contaminating drinking water, and downstream effects such as dead zones caused by agricultural runoff is concentrated in large water bodies.

Agricultural microbiology is a branch of microbiology dealing with plant-associated microbes and plant and animal diseases. It also deals with the microbiology of soil fertility, such as microbial degradation of organic matter and soil nutrient transformations. The primary goal of agricultural microbiology is to comprehensively explore the interactions between beneficial microorganisms like bacteria and fungi with crops. It also deals with the microbiology of soil fertility, such as microbial degradation of organic matter and soil nutrient transformations.

Soil management is the application of operations, practices, and treatments to protect soil and enhance its performance. It includes soil conservation, soil amendment, and optimal soil health. In agriculture, some amount of soil management is needed both in nonorganic and organic types to prevent agricultural land from becoming poorly productive over decades. Organic farming in particular emphasizes optimal soil management, because it uses soil health as the exclusive or nearly exclusive source of its fertilization and pest control.

The Indian Institute of Soil Science is an autonomous institute for higher learning, established under the umbrella of Indian Council of Agricultural Research (ICAR) by the Ministry of Agriculture, Government of India for advanced research in the field of soil sciences.

<span class="mw-page-title-main">Regenerative agriculture</span> Conservation and rehabilitation approach to food and farming systems

Regenerative agriculture is a conservation and rehabilitation approach to food and farming systems. It focuses on topsoil regeneration, increasing biodiversity, improving the water cycle, enhancing ecosystem services, supporting biosequestration, increasing resilience to climate change, and strengthening the health and vitality of farm soil.

<span class="mw-page-title-main">Soil regeneration</span> Creation of new soil and rejuvenation of soil health

Soil regeneration, as a particular form of ecological regeneration within the field of restoration ecology, is creating new soil and rejuvenating soil health by: minimizing the loss of topsoil, retaining more carbon than is depleted, boosting biodiversity, and maintaining proper water and nutrient cycling. This has many benefits, such as: soil sequestration of carbon in response to a growing threat of climate change, a reduced risk of soil erosion, and increased overall soil resilience.

<span class="mw-page-title-main">Carbon farming</span> Agricultural methods that capture carbon

Carbon farming is a set of agricultural methods that aim to store carbon in the soil, crop roots, wood and leaves. The technical term for this is carbon sequestration. The overall goal of carbon farming is to create a net loss of carbon from the atmosphere. This is done by increasing the rate at which carbon is sequestered into soil and plant material. One option is to increase the soil's organic matter content. This can also aid plant growth, improve soil water retention capacity and reduce fertilizer use. Sustainable forest management is another tool that is used in carbon farming. Carbon farming is one component of climate-smart agriculture. It is also one way to remove carbon dioxide from the atmosphere.

Seaweed fertiliser is organic fertilizer made from seaweed that is used in agriculture to increase soil fertility and plant growth. The use of seaweed fertilizer dates back to antiquity and has a broad array of benefits for the soils.

Soil carbon sponge is porous, well-aggregated soil in good health, better able to absorb and retain water. Australian microbiologist and climatologist, Walter Jehne, articulated the concept of the soil carbon sponge in his 2017 paper, Regenerate Earth, connecting soil carbon with a restored water cycle able induce planetary cooling through evaporative cooling and higher reflectance of denser green vegetation. Cooling from increased cloud formation is another benefit of soil regeneration anticipated by Jehne.

References

  1. ↑ NRCS 2013
  2. ↑ "Soil Quality | NRCS Colorado". Archived from the original on 2017-01-23. Retrieved 2018-03-21.
  3. ↑ Schlesinger, William H.; Amundson, Ronald (June 2018). "Managing for soil carbon sequestration: Let's get realistic". Global Change Biology. 25 (2): 386–389. doi: 10.1111/gcb.14478 . PMID   30485613.
  4. ↑ Nannipieri, P.; Ascher, J.; Ceccherini, M. T.; Landi, L.; Pietramellara, G.; Renella, G. (December 2003). "Microbial diversity and soil functions" (PDF). European Journal of Soil Science. 54 (4): 655–670. Bibcode:2003EuJSS..54..655N. doi:10.1046/j.1351-0754.2003.0556.x. S2CID   247671645. Archived (PDF) from the original on 2016-04-12.
  5. ↑ The Role of Soil Biology in Improving Soils Archived 2014-03-12 at the Wayback Machine Webinar
  6. ↑ "Listing 17 microbes and their effects on the soil and plant health functions". Explogrow, Dr Malherbe, BSc, BSc Hons., MSc, Pr.Sci.Nat. 22 December 2016. Archived from the original on 25 June 2016.
  7. ↑ "Healthy Soil". www.highbrixgardens.com. Archived from the original on 19 December 2016. Retrieved 26 April 2018.
  8. ↑ Kick, Chris (18 February 2014). "New soil test measures soil health - Farm and Dairy". farmanddairy.com. Archived from the original on 1 December 2017. Retrieved 26 April 2018.
  9. ↑ Bagnall, Dianna K.; Rieke, Elizabeth L.; Morgan, Cristine L. S.; Liptzin, Daniel L.; Cappellazzi, Shannon B.; Honeycutt, C. Wayne (2023-03-01). "A minimum suite of soil health indicators for North American agriculture". Soil Security. 10: 100084. Bibcode:2023SoSec..1000084B. doi: 10.1016/j.soisec.2023.100084 . ISSN   2667-0062.
  10. ↑ Roper, Wayne R.; Osmond, Deanna L.; Heitman, Joshua L.; Wagger, Michael G.; Reberg-Horton, S. Chris (January 2017). "Soil Health Indicators Do Not Differentiate among Agronomic Management Systems in North Carolina Soils". Soil Science Society of America Journal. 81 (4): 828–843. Bibcode:2017SSASJ..81..828R. doi: 10.2136/sssaj2016.12.0400 .
  11. ↑ Bernard T. Nolan; et al. (January 1998). "A National Look at Nitrate Contamination of Ground Water". Water Conditioning and Purification. 39 (12): 76–79. Archived from the original on 2014-03-13.
  12. ↑ Estimating Soil Carbon, Nitrogen, and Phosphorus Mineralization from Short-Term Carbon Dioxide Respiration Communications. in Soil Science and Plant Analysis, 39: 2706–2720, 2008
  13. ↑ Soil CO2 respiration: Comparison of chemical titration, CO2 IRGA analysis and the Solvita gel system. Renewable Agriculture and Food Systems: 23(2); 171–176
  14. 1 2 3 Jayasinghe, Sadeeka L.; Thomas, Dean T.; Anderson, Jonathan P.; Chen, Chao; Macdonald, Ben C. T. (14 November 2023). "Global Application of Regenerative Agriculture: A Review of Definitions and Assessment Approaches". Sustainability. 15 (22): 15941. doi: 10.3390/su152215941 . ISSN   2071-1050.
  15. 1 2 3 4 Mays, Daniel (10 November 2020). The No-Till Organic Vegetable Farm: How to Start and Run a Profitable Market Garden That Builds Health in Soil, Crops, and Communities. North Adams, MA: Storey Publishing, LLC.{{cite book}}: CS1 maint: date and year (link)
  16. 1 2 Khangura, Ravjit; Ferris, David; Wagg, Cameron; Bowyer, Jamie (2023-01-27). "Regenerative Agriculture—A Literature Review on the Practices and Mechanisms Used to Improve Soil Health". Sustainability. 15 (3): 2338. doi: 10.3390/su15032338 . ISSN   2071-1050.
  17. 1 2 3 4 Schon, Nicole; Fraser, Trish; Masters, Nicole; Stevenson, Bryan; Cavanagh, Jo; Harmsworth, Garth; Grelet, Gwen-Aelle (2024-06-21). Soil health research in the context of regenerative agriculture (Report). AgResearch.
  18. 1 2 Spiegal, Bill (18 March 2016). "Investing In Soil Health Pays". Successful Farming. Retrieved 2024-12-08.
  19. ↑ M. Tahat, Monther; M. Alananbeh, Kholoud; A. Othman, Yahia; I. Leskovar, Daniel (15 June 2020). "Soil Health and Sustainable Agriculture". Sustainability. 12 (12): 4859. doi: 10.3390/su12124859 . ISSN   2071-1050.
  20. ↑ Zhang, Qian Forrest (6 November 2024). "From Sustainable Agriculture to Sustainable Agrifood Systems: A Comparative Review of Alternative Models". Sustainability. 16 (22): 9675. doi: 10.3390/su16229675 . ISSN   2071-1050.
  21. 1 2 Leng, Vira; Cardinael, Rémi; Tivet, Florent; Seng, Vang; Mark, Phearum; Lienhard, Pascal; Filloux, Titouan; Six, Johan; Hok, Lyda; Boulakia, Stéphane; Briedis, Clever; de Moraes Sá, João Carlos; Thuriès, Laurent (2024-10-10). "Diachronic assessment of soil organic C and N dynamics under long-term no-till cropping systems in the tropical upland of Cambodia". SOIL. 10 (2): 699–725. Bibcode:2024SOIL...10..699L. doi: 10.5194/soil-10-699-2024 . ISSN   2199-3971.
  22. ↑ Rani, Meenu; Chaudhary, Bhagwan Singh; Jamal, Saleha; Kumar, Pavan (2022-09-08). Towards Sustainable Natural Resources: Monitoring and Managing Ecosystem Biodiversity. Springer Nature. ISBN   978-3-031-06443-2.
  23. ↑ Rehberger, Emily; West, Paul; Spillane, Charles; McKeown, Peter (31 May 2023). "What climate and environmental benefits of regenerative agriculture practices? An evidence review". Environmental Research Communications. 5 (5). Bibcode:2023ERCom...5e2001R. doi:10.1088/2515-7620/acd6dc – via IOPscience.
  24. ↑ "What are the Benefits of Compost". U.S. Composting Council.
  25. ↑ Maharjan, Bijesh; Das, Saurav; Acharya, Bharat Sharma (2020-09-01). "Soil Health Gap: A concept to establish a benchmark for soil health management". Global Ecology and Conservation. 23: e01116. Bibcode:2020GEcoC..2301116M. doi: 10.1016/j.gecco.2020.e01116 . ISSN   2351-9894.

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