Science - USA (2022-03-04)

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RESTORATION ECOLOGY

Soil microbiota as game-changers in restoration

of degraded lands

Oksana Coban*, Gerlinde B. De Deyn, Martine van der Ploeg

BACKGROUND:Soil, the living skin of Earth,
provides ecosystem services critical for life:
Soil acts as a filter and store of water, pro-
vides a growing medium that supplies plants
and heterotrophs with water and nutrients,
offers habitat for a large diversity of organ-
isms, and is the source of most of our anti-
biotics. Humanity is increasingly challenged
by the combination of climate change, popu-
lation growth, and land degradation, including
carbon loss, biodiversity decline, and erosion.
In particular, land degradation reduces soil
hydrological functioning and thereby several
other ecosystem services. Such impacts occur
through alterations of hydraulic functioning,
infiltration and soil moisture storage, carbon
cycling, biological activity, transport of nu-
trients and contaminants, and plant growth.
Impacts of global environmental change and
associated soil degradation need to be un-
derstood and reversed as biodiversity, food
production, climate regulation, and people’s
livelihoods are increasingly affected by soil

ecosystem degradation. The interplay between

soil biota and soil hydrological functioning

plays an essential role in many biogeochemical

cycles, including the water and carbon cycles.

Microorganisms dominate soil life and per-

form an array of vital soil functions by reg-

ulating nutrient cycling, decomposing organic

matter, defining soil structure, suppressing

plant diseases, and supporting plant produc-

tivity. The presence of microorganisms and

their activity can affect soil structure and hy-

draulic properties in multiple ways. Case studies

indicate the potential of microorganisms as

game-changers toward the restoration of soil

functioning. However, the role of soil micro-

biota in forming and sustaining soils has his-

torically been overlooked.

ADVANCES:It has been proposed that micro-

bial communities not only are an indicator

of ecosystem health and restoration level

but also can be manipulated to enhance the

recovery of degraded ecosystems. In the past

decade, there have been an increasing num-

ber of studies suggesting the use of micro-

organisms as ecosystem mediators, particularly

to enhance crop production and to engineer

microorganisms for dryland restoration. Most

current experimental approaches focus on

monitoring changes in the microbial com-

munity that can be correlated with land res-

toration; however, microorganisms are also

facilitators of ecosystem change, not just fol-

lowers. We review how microorganisms can

help address different types of land degra-

dation, with a focus on physical soil loss and

transformation, loss of soil chemical proper-

ties, and contamination. We discuss potentially

the most valuable groups of microorganisms

for soil restoration (namely, plant growth–

promoting rhizobacteria, nitrogen-fixing bacte-

ria, and mycorrhizal fungi), emphasizing

drylands and advances in plant-microbe in-

teraction studies. We review known effects

of microorganisms on soil physical and, spe-

cifically, hydraulic properties at pore scale

and discuss future strategies for the long-

term restoration of degraded lands. We also

identify the methodological challenges that

have so far hampered progress in understand-

ing soil biophysical processes.

OUTLOOK:Microorganisms can play the lead-

ing role in restoring degraded lands, improv-

ing soil hydraulic properties such as infiltration

and water retention and reducing soil hydro-

phobicity, which together can facilitate eco-

system restoration. We advocate for research

on mechanisms to restore degraded soils with

the use of microorganisms. Given the critical

role of freshwater availability to terrestrial life

and the paucity of studies on hydrological res-

toration, we especially advocate for research

on the hydrological restoration of degraded

soil using microorganisms. We propose that

microorganisms can improve soil hydraulic

properties such as infiltration and water re-

tention and reduce soil hydrophobicity. Along

with new organic matter derived from mi-

crobes, this will promote plant growth and

facilitate further ecosystem restoration. Such

a restoration strategy requires collaboration

across the research fields of microbiology

and soil hydrology, of which there has been

very little to date. Understanding the dynam-

ics of soil microbes and connected hydrolog-

ical processes would create the foundation for

restoration practices that can return resilience

to the soil ecosystem.▪

RESEARCH

990 4 MARCH 2022•VOL 375 ISSUE 6584 science.orgSCIENCE

Department of Environmental Sciences, Wageningen

University & Research, Wageningen, Netherlands.

*Corresponding author. Email: [email protected]

Cite this article as O. Cobanet al.,Science 375 , eabe0725

(2022). DOI: 10.1126/science.abe0725

READ THE FULL ARTICLE AT

https://doi.org/10.1126/science.abe0725

Degraded land in Libya.In degraded lands, a decrease in soil nutrients and organic matter, deterioration of
soil structure, increase in salinity, water deficiency, and physical instability can be observed. CREDIT:CINOBY/ISTOCKPHOTO