Ecological Restoration: Why Soil Health Matters

The urgency of ecological restoration is undeniable amidst escalating ecosystem degradation and habitat loss, exacerbated by human activities and climate change. Deforestation, urbanization, and mining have left many ecosystems on the brink, while the remaining natural habitats, crucial for plant and animal populations, are often degraded and fragmented.

Effective restoration necessitates a comprehensive approach, acknowledging the diverse levels of degradation and adapting strategies accordingly. The severity of degradation varies significantly, from areas with severely compromised vegetation and soil to those retaining much of their ecological integrity. Notably, approximately 75% of global soils suffer from degradation, with human land use causing persistent physicochemical and biological impacts that are challenging to reverse.

Restoration typically aims to reinstate a self-sustaining ecosystem resembling reference conditions, re-establishing native species and natural processes in less severe cases. However, where native vegetation and soil are nearly lost, goals may be more modest, focusing on soil health improvement, vegetation cover increase, and enhanced ecosystem functions like water retention and nutrient cycling.

Soil health, which is increasingly recognized as essential for successful ecosystem restoration, is often neglected in practice. This is partly due to the difficulty of assessing soil health, which refers to the soil's ability to support essential functions that maintain the well-being of the ecosystem. Unlike easily measured soil properties such as pH, nutrient content, or organic matter levels, soil health is a broader concept that can be challenging to define and measure. A key challenge is that soil health can only be evaluated in relation to the desired condition of a specific ecosystem, which requires knowledge of a suitable reference ecosystem that may not always exist or be accessible.

Healthy soils are characterized by their strong connection and feedback with the aboveground community, which together sustain ecosystem functions. They typically have a well-structured profile with adequate pore spaces for air, water, nutrients, roots, and soil organisms. They also contain organic matter and essential nutrients in the right proportions to support native plant growth. Recent studies have highlighted the importance of the composition and diversity of soil biota, including microorganisms and soil fauna, which regulate the cycling of organic matter, nutrients, and soil structure maintenance. Additionally, healthier soils tend to have lower levels of compaction and greater aggregation, allowing for deep root growth, efficient water infiltration, and prevention of topsoil and nutrient loss. These attributes provide the foundation for strong aboveground-belowground interactions, ecosystem resilience to environmental stressors, and ecosystem services such as carbon sequestration, water purification, and support for biodiversity.

The role of aboveground and belowground linkages

In healthy ecosystems, aboveground and belowground components interact in complex ways, primarily through roots and litter, creating positive feedback loops that enhance resilience and productivity. Roots absorb nutrients, release exudates, and form symbiotic relationships with beneficial organisms, while litter provides organic matter and nutrients to the soil.

Land degradation disrupts these interactions. It negatively impacts root growth, exudation, and symbiotic relationships, leading to a decline in soil health and nutrient cycling. Degradation also alters litter input and quality, affecting soil structure and fertility. These changes can create a feedback loop that favors invasive species and further degrades the ecosystem.

Furthermore, land degradation disrupts the soil food web, affecting critical interactions between plants, microbes, and soil fauna. Soil fauna play key roles in decomposition, nutrient cycling, and soil structure maintenance. Their decline in degraded soils negatively impacts plant growth and ecosystem recovery.

Effective restoration efforts must consider these complex interactions and prioritize reestablishing soil health, including the soil food web, to ensure long-term ecosystem resilience and success.

Ecological restoration projects must consider the health of soil communities and the processes that support ecosystem function for successful, holistic results. Revegetating degraded areas without improving soil health, specifically the microorganisms and invertebrates that drive nutrient cycles, will likely lead to incomplete restoration. Research shows that soil microbial recovery is often slow and incomplete after restoration, even with revegetation.

Interventions to promote soil health

The level of degradation will determine the type and intensity of interventions required to meet restoration goals. Highly degraded systems often require intensive early-stage interventions, such as soil management and site preparation to alleviate compaction. Applying amendments and nutrients can improve soil health and plant establishment. As ecosystems progress toward their target conditions, the focus may shift to simpler management practices (eg, weed control, thinning, and deposition of coarse woody debris) to enhance ecosystem functions and long-term stability. 

Soil health is paramount for the success of ecological restoration projects. It is the foundation of ecosystem functioning, resilience, and biodiversity. Healthy soils provide a supportive environment for plant growth, enhance water regulation and quality, promote biodiversity, and contribute to climate change mitigation. By prioritizing soil health, restoration projects can create sustainable ecosystems that are better equipped to withstand environmental stressors and support life on Earth. Investing in soil health is an investment in the future of our planet and the well-being of generations to come.