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1Volume 110 | Number 5/6
May/June 2014
South African Journal of Science
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News & Views Understanding soil health in South Africa
Page 1 of 4
The unknown underworld:
Understanding soil health in South Africa
The need to provide food security to a growing human population in the face of global threats such as climate
change, land transformation, invasive species and pollution1 is placing increasing pressure on South African soils.
South Africa is losing an estimated 300–400 million tonnes of soil annually2, while soil degradation is a major threat
to agricultural sustainability3. In spite of these problems, treatment of soil health in biodiversity assessment and
planning in South Africa has been rudimentary to date.4,5
Defining soil health
Soil is a crucial component of the pedosphere, which sustains life, and should therefore be regarded as one of the
most important assets held by South Africans. However, in South Africa, soil is a highly neglected research focus
in ecosystem service delivery. Studies of ecosystem services often focus on more elegant and tractable systems,
such as pollination networks.6 Currently in South Africa, soils are viewed in certain sectors as resources that can
be used to generate short-term gains, rather than assets to be protected and developed. Soils form the basis for
food security through agriculture, where processes taking place in the pedosphere result in water retention, nutrient
augmentation and soil biodiversity proliferation.
In an effort to facilitate research on soil health, or at least stimulate debate on the topic, we propose that soil
health be measured by a combination of abiotic (A) and biotic (B) and socio-economic (S) aspects relative to a
benchmark measure, i.e.
Soil health = ∑A. ∑B. ∑S
benchmark
where A is measured by a subset of soil physicochemical indicators (with subsets determined on the basis of
variable thresholds relating to soil type and soil usage); B is determined by standard biodiversity metrics (e.g.
species richness, abundance, network or species assemblage connectedness), incorporating biodiversity in
the context of applied strategies (e.g. agricultural push–pull systems and mixed cropping) and S is determined
by socio-economic values (e.g. monetary value, equity, human well-being). In order to scale each component,
benchmark values will also have to be determined that will serve as the denominator for calculation of changing
component values over time.7,8
Here we use a similar model to that used in above ground environmental analyses (e.g. the IUCN’s system analysis
in Leverington et al.9), but we recognise that the below ground ‘closed’ medium functions at different tempos
and scales. As such, this model is simplistic, yet a degree of ignorance exists about ‘understanding’ soils,10
strengthening the notion that soils need to be elevated to mainstream research foci where interactions among
the physical, chemical and biological components of soils receive precedence and serve as a point of departure.
For soils to operate in a complex, interacting total system manner, biodiversity in different environments serving
different socio-economic requirements can potentially be temporally and spatially separated, e.g. hydroponic farms
and conservation areas or an ecological network in which all aspects are incorporated. In some cases this can
lead to an overall greater soil health set-up than if all elements were combined in one area at a specific time period
(e.g. debate on conservation versus agriculture, or conservation and agriculture11 and landscape-scale analysis
over seasons12).
The three components of soil defined here all contribute to ecosystem services and intersect to provide healthy
soils. The model for this soil health index (Figure 1), supported by intersection descriptions and more detailed
relevant examples (Figure 2), serves to emphasise that soils are extremely complex and function in multiple
roles, and as such have a pivotal role in ecological function. Based on this framework, we formulated several key
research questions (Table 1).
The need for foundational work on soil organisms
In the last decade, the diverse roles of soil communities in the ecological function of soils has gained global
recognition.13 Several large multidisciplinary projects in Europe (such as ENVASSO and EcoFINDERS) now
focus on soil organisms using holistic approaches incorporating traditional taxonomy14 and modern molecular
techniques15. However, in South Africa, like elsewhere in the world, research in the field of soil biology has been
neglected compared with research in soil chemistry or soil physics. This scenario has started to change over the
past decade or two and South Africa is no exception in this regard. Research on a broad biological basis regarding
South African soils has increased since the mid-1990s and these outcomes are published in journals such as the
European Journal of Soil Science, Soil Biology and Biochemistry, Biogeochemistry, Soil Research, Geoderma and
the South African Journal of Plant and Soil. Sadly, however, this cannot be said of pure foundational research on
soil organisms and, despite some notable pioneering experts (e.g. Lawrence16), our knowledge of South African
soil organisms is largely restricted to taxonomically well-known groups such as ants17-19 and spiders20, and even
then this knowledge is often fragmented and poorly documented. The need to integrate existing research initiatives
was unanimously expressed at a Soil Health Workshop at the XVII Congress of the Entomological Society of
Southern Africa in July 2011. This expression led to the formation of SERG (Soil Ecosystem Research Group) – a
soil biodiversity research group that provides a platform for linking and promoting research on soil organisms.
AUTHORS:
Schalk v.d.M. Louw1
John R.U. Wilson2,3
Charlene Janion3
Ruan Veldtman2,4
Sarah J. Davies3
Matthew Addison4,5
AFFILIATIONS:
1Department of Zoology and
Entomology, University of
the Free State, Bloemfontein,
South Africa
2South African National
Biodiversity Institute,
Kirstenbosch National
Botanical Gardens, Cape Town,
South Africa
3Centre for Invasion Biology,
Department of Botany and
Zoology, Stellenbosch University,
Stellenbosch, South Africa
4Department of Conservation
Ecology and Entomology,
Stellenbosch University,
Stellenbosch, South Africa
5Hortgro Science, Stellenbosch,
South Africa
CORRESPONDENCE TO:
Schalk Louw
EMAIL:
louws@ufs.ac.za
POSTAL ADDRESS:
Department of Zoology and
Entomology, University of
the Free Sate, PO Box 339,
Bloemfontein 9300, South Africa
KEYWORDS:
soil signature; edaphic factors;
sustainability; food security;
sustainable agriculture
HOW TO CITE:
Louw SvdM, Wilson JRU,
Janion C, Veldtman R, Davies
SJ, Addison M. The unknown
underworld: Understanding soil
health in South Africa. S Afr J Sci.
2014;110(5/6), Art. #a0064, 4
pages. http://dx.doi.org/10.1590/
sajs.2014/a0064
© 2014. The Authors.
Published under a Creative
Commons Attribution Licence.
2Volume 110 | Number 5/6
May/June 2014
South African Journal of Science
http://www.sajs.co.za
News & Views Understanding soil health in South Africa
Page 2 of 4
Conceptual model Area Definition Examples
ABS
Happy healthy soils – production landscapes
where the inputs are minimal and biodiversity
is maintained through sustained soil ecosystem
service delivery
Sustainable flower har vesting from the wild
(Figure 2)
Mixed cropping system with conservation tillage
AB
Ecological function – natural ecosystems with
significant functional roles. Ecological processes
and physicochemical cycles are maintained; soil
condition is preserved
Wetlands
Unfarmed Succulent Karoo ecosystems –
dry low primary productivity regions with
low or no animal stocking (Figure 2)
BS
Beneficial organisms – soil organisms are used
by humans for utilitarian purposes
Biological control (e.g. entomo-pathogenic
nematodes) and vermi-composting
Bio-prospecting
AS
Input production – production systems
where physical and chemical properties are
manipulated to maintain production
Mono-cultural intensive agriculture
B
Biotic – soil biodiversity, including organisms
of all different taxonomic and functional groups,
which together result in multi-trophic interactions
Maputo-Pondoland Centre of Endemism
AAbiotic – physical and chemical properties of soil Iron oxide rich Kalahari sandy soils
SSocio-economic – encompasses ownership and
land use and subsequent production
Hydroponics (Figure 2)
Figure 1: Proposed conceptual scheme for defining soil. We consider healthy soils as those that provide abiotic, biotic and socio-economic services.
Hydroponics Nature reserves in the Succulent Karoo Sustainable harvesting of wild flowers
Approximately 800 ha of hydroponics in RSA in 200221 Knersvlakte Nature Reserve: 24 058 ha22 South Africa’s Agulhas Plain: 30 597 ha23
S
B
AAB
BS
B
AB
BS
AB∩S
Productivity via hydroponics, means there is no ‘soil’
at all.24 However, such systems have no ecosystem
functionality. A neighbouring/interlinked soil system
is required for soil processes to continue. System will
require continual inputs.
Succulent Karoo soils are likely to harbour many
endemic species,25 although they have been poorly
studied to date. There are some important functions,
e.g. reducing erosion, but very little productive value
exists, and in many cases such soils are sensitive
to disturbance.26
Several initiatives are in place to combine economic
value with biodiversity conservation. The selling
of flowers (particularly Proteaceae) from nature
reserves as ‘green’ products raises money for
environmental restoration and management, as well
as local development.
Figure 2: Case studies highlighting how ‘soils’ differ in abiotic, biotic and socio-economic aspects (based on examples from Figure 1).
Socio-economic
(S)
Beneficial
organisms
Happy
healthy soils
Input
production
Abiotic
(A)
Ecological
function
Biotic
(B)
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One of the first priorities identified by SERG was the need to collate and
mobilise data and collections to consolidate and compare the state of
knowledge of each group.
Conclusion
We anticipate that research on soils will be a major initiative linking
fundamental and applied research endeavours in the times ahead,
especially in the context of climate smart management strategies.
Having said this, we do recognise that the establishment of thresholds
for biological indicators of soil health is a far greater challenge than the
establishment of thresholds for either chemical or physical indicators of
soil health, simply because biological indicators are too variable over
short periods. Future research endeavours will therefore have to breach
this complication.
Acknowledgements
We thank our respective institutions and departments for suppor t in
terms of funding and facilities. We also thank the NRF for funding. An
anonymous reviewer is gratefully acknowledged for providing many
positive and thought-provoking comments which helped improve
the manuscript.
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Interaction and feedback loops between plants and soil organisms that affect nutrient cycling.
Interaction and feedback loops between soil nutrient cycling processes and crop yield.
Identification of soil organisms and their nutrient processing qualities.
Quantification of nutrient cycles.
Identification of species assemblages most beneficial to soil processes and crop yield.
News & Views Understanding soil health in South Africa
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News & Views Understanding soil health in South Africa
Page 4 of 4
... But the necessity of providing food security to a growing human population in the face of climate change, land transformation, biological invasions and pollution (MEA, 2005) is placing increasing pressure on South African soils. Research is urgently needed to understand how abiotic, biotic, and socioeconomic factors interact to affect soil health in southern Africa, with the lack of integrated knowledge on soil biodiversity in the region posing a major current limitation to such understanding (Louw et al., 2014). ...
... With around a quarter of the world's biodiversity hotspots, more Africa-based taxonomists are needed. In South Africa, the need to integrate existing information and work collectively led to the formation of the Soil Ecosystem Research Group (SERG) with the aim to provide a platform for linking and promoting research on soil organisms (Louw et al., 2014). One of the first priorities identified was the need to collate and mobilise data and collections such that the state of knowledge of each group can be consolidated and compared. ...
... In particular, intensified land-use is a threat to soil biodiversity globally (Tsiafouli et al., 2015), and in South Africa (Scholtz and Chown, 1993). The livelihoods of people in South Africa depend in many ways on the continued functioning of the soil ecosystem, so there is an urgent need for basic biodiversity knowledge in order to facilitate the soil ecosystem research required to assess sustainability (Louw et al., 2014). There are clearly some commonalities in how soil biota have been sampled. ...
... However, global change drivers and their synergistic effects (Millennium Ecosystem Assessment 2005) might cause extinctions of species not even known to science (Essl et al. 2013;Costello et al. 2013). One aspect that has often been overlooked is the significant contribution of soil fauna to soil health, below ground diversity, and more broadly to ecosystem functioning (Wardle 2002, Wardle et al. 2004, Louw et al. 2014. ...
... The need to enlarge South Africa's capacity to answer applied and basic research questions on the roles and impacts of earthworms in the functioning of natural ecosystems was unanimously agreed upon during a workshop on soil organisms at the XVII Congress of the Entomological Society of Southern Africa (July 2011), and separately by the CAPE Invasive Alien Animal Working Group (May 2011) (Louw et al. 2014). ...
... To build our ecological and taxonomic knowledge of soil fauna in South Africa, studies of soil organisms need more coordination (Louw et al. 2014). In order to do this, one needs to move away from traditional ad hoc sampling to more coordinated, standardised sampling for comparison with other studies. ...
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... This knowledge will in future become increasingly important as environmental conditions change as a result of climate and other changes. Soil is a service-providing asset under growing pressure (vdM Louw et al. 2014). It is home to an array of species of soil invertebrates which is enormous, encompassing virtually all terrestrial invertebrate phyla. ...
... This, in turn, influences the productivity of the soil, along with its resilience (i.e. the capacity of the soil to return to a normal state after a perturbation; see Mitchell et al. 2000), and its ability to provide other important ecosystem services (Woomer & Swift 1994;Robinson et al. 2012). In general, there is limited knowledge on the diversity of soil fauna and their linkage to the entire ecosystem structure and functioning (Warren & Zou 2002;Barrios 2007) and baseline information (regarding diversity, assemblage composition and their responses to environmental and anthropogenic factors) on this diverse group of organisms is lacking (Louw et al. 2014;Janion-Scheepers et al. 2016). ...
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Principles and methods of landscape ecology are intensively used to model and to manage disturbed landscapes and menaced pristine areas as well. Students and professionals can find a new version of "Principles and Methods in Landscape Ecology" firstly published in 1998 by Chapman & Hall (London). Landscape ecology is an integrative and multi-disciplinary science and "Principles and Methods in Landscape Ecology" reconciles the geological, botanical, zoological and human perspectives. In particular new paradigms and theories like percolation, metapopulation, hierarchies, source-sink models, have been integrated, in this last edition, with the recent theories on bio-complexity, information and cognitive sciences. Methods for studying landscape ecology are covered including spatial geometry models and remote sensing in order to create confidence toward techniques and approaches that require a high experience and long-time dedication. Principles and Methods in Landscape Ecology is a textbook useful to present the landscape in a multi-vision perspective for undergraduate and graduate students of biology, ecology, geography, forestry, agronomy, landscape architecture and planning. Sociology, economics, history, archaeology, anthropology, ecological psychology are some sciences that can benefit of the holistic vision offered by this texbook. A relevant goal of this second edition is to increase confidence in the new generations of students and practitioners for considering the ecological systems as the result of the integration between ecosystemic (non spatial) and landscape (spatial) patterns and processes.
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Nearly half the world's vascular plant species and one-third of terrestrial vertebrates are endemic to 25 “hotspots” of biodiversity, each of which has at least 1500 endemic plant species. None of these hotspots have more than one-third of their pristine habitat remaining. Historically, they covered 12% of the land's surface, but today their intact habitat covers only 1.4% of the land. As a result of this habitat loss, we expect many of the hotspot endemics to have either become extinct or—because much of the habitat loss is recent—to be threatened with extinction. We used World Conservation Union [ IUCN ] Red Lists to test this expectation. Overall, between one-half and two-thirds of all threatened plants and 57% of all threatened terrestrial vertebrates are hotspot endemics. For birds and mammals, in general, predictions of extinction in the hotspots based on habitat loss match numbers of species independently judged extinct or threatened. In two classes of hotspots the match is not as close. On oceanic islands, habitat loss underestimates extinction because introduced species have driven extinctions beyond those caused by habitat loss on these islands. In large hotspots, conversely, habitat loss overestimates extinction, suggesting scale dependence (this effect is also apparent for plants). For reptiles, amphibians, and plants, many fewer hotspot endemics are considered threatened or extinct than we would expect based on habitat loss. This mismatch is small in temperate hotspots, however, suggesting that many threatened endemic species in the poorly known tropical hotspots have yet to be included on the IUCN Red Lists. We then asked in which hotspots the consequences of further habitat loss (either absolute or given current rates of deforestation) would be most serious. Our results suggest that the Eastern Arc and Coastal Forests of Tanzania-Kenya, Philippines, and Polynesia-Micronesia can least afford to lose more habitat and that, if current deforestation rates continue, the Caribbean, Tropical Andes, Philippines, Mesoamerica, Sundaland, Indo-Burma, Madagascar, and Chocó–Darién–Western Ecuador will lose the most species in the near future. Without urgent conservation intervention, we face mass extinctions in the hotspots. Resumen: Casi la mitad del total de plantas vasculares del mundo y un tercio de los vertebrados terrestres son endémicos en 25 “áreas críticas” para la biodiversidad, cada una de las cuales tiene por lo menos 1500 especies de plantas endémicas. En ninguno de estos sitios permanece más de un tercio de su hábitat prístino. Históricamente, cubrían 12% de la superficie terrestre, pero en la actualidad su hábitat intacto cubre solo 1.4% del terreno. Como resultado de esta pérdida de hábitat esperamos que muchas de las especies endémicas a estos sitios estén extintas o – porque la pérdida de hábitat es reciente – se encuentren amenazadas de extinción. Utilizamos Listas Rojas de UICN para comprobar esta predicción. En general, entre la mitad y dos tercios de las plantas amenazadas y el 57% de los vertebrados terrestres amenazados son endémicos de áreas críticas para la biodiversidad. Para aves y mamíferos en general, las predicciones de extinción en las áreas críticas para la biodiversidad, basadas en la pérdida de hábitat, coinciden con el número de especies consideradas extintas o amenazadas independientemente. En dos clases de áreas críticas para la biodiversidad la coincidencia no es muy grande. En islas oceánicas, la pérdida de hábitat subestima la extinción porque las especies introducidas han causado más extinciones que las producidas por la reducción del hábitat. Por lo contrario, la pérdida de hábitat sobrestima la extinción en áreas críticas para la biodiversidad extensas, lo que sugiere una dependencia de escala (este efecto también es aparente para plantas). Para reptiles, anfibios y plantas mucho menos especies endémicas son consideradas amenazadas o extintas por pérdida de hábitat. Sin embargo, esta discordancia es pequeña en áreas críticas para la biodiversidad en zonas templadas templadas, lo que sugiere que muchas especies endémicas amenazadas en las poco conocidas áreas críticas para la biodiversidad en zonas tropicales aun están por incluirse en las Listas Rojas. Posteriormente nos preguntamos en que áreas críticas para la biodiversidad serían más serias las consecuencias de una mayor pérdida de hábitat (absoluta o con las tasas actuales de deforestación). Nuestros resultados sugieren que el Arco Oriental y los Bosques Costeros de Tanzania/Kenia, Filipinas, Polinesia/Micronesia no pueden soportar mayores pérdidas y que, si continúan las tasas de deforestación actuales, el Caribe, Andes Tropicales, Filipinas, Mesoamérica, Sundaland, Indo-Burma, Madagascar y Chocó/Darién/Ecuador Occidental perderán más especies en el futuro. Sin acciones urgentes de conservación, habrá extinciones masivas en las áreas críticas para la biodiversidad.