The Dual Nature of Natural Hazards: Destruction and Service Functions

Natural hazards are rarely just one thing. A volcanic eruption buries farmland and chokes rivers with ash – yet that same ash rebuilds soil fertility for generations. A wildfire tears through a forest – yet it also clears the deadwood that was suppressing new growth. This dual nature is not a paradox; it is how Earth’s systems have always worked. To understand natural hazards fully, we need to look beyond the immediate destruction and examine both the cascading layers of damage and the surprising ecological services these events provide.

The ripple effect: primary, secondary, and tertiary impacts 🔗

When a natural hazard strikes, its consequences do not stop with the initial event. Research published by IntechOpen categorizes these impacts into three distinct levels, each unfolding over a different timeframe and affecting communities and ecosystems in different ways.

Primary effects 🔗

Primary effects are the direct, immediate consequences of the hazard itself. According to AG Global Strategies, these occur as a direct result of the natural process – the collapse of a building during an earthquake, water damage from a flood, or the destruction of crops by volcanic lava. They are the most visible outcomes and typically happen during or within hours of the event. In an earthquake, this means ground shaking, structural collapse, and casualties. In a flood, it means inundation of land, destruction of infrastructure, and displacement of people.

Secondary effects 🔗

Secondary effects arise as a consequence of primary damage, unfolding over days, weeks, or even months. As the Times Group explains, examples include fires ignited after earthquakes, disease outbreaks following floods due to contaminated water, economic downturns from damaged supply chains, and psychological trauma in survivors. A particularly illustrative example: when an earthquake ruptures water pipes (primary effect), cholera outbreaks can follow as communities lose access to clean water (secondary effect). These indirect consequences often complicate recovery efforts and extend the period of crisis far beyond the initial disaster.

Tertiary effects 🔗

Tertiary effects are the long-term, indirect outcomes that reshape communities and ecosystems over years or decades. The SEG Wiki on Natural Disasters and Hazards lists these as changes in the landscape, long-term habitat loss, and crop failures caused by altered temperatures or soil conditions. At the societal level, tertiary effects can include permanent demographic shifts – populations that never return to hazard-prone areas – as well as lasting changes to local economies and land-use patterns. These are often the hardest effects to measure, yet they have the most enduring impact on both human societies and natural ecosystems.

Service functions of natural hazards 🔗

Beyond their destructive consequences, natural hazards perform ecological functions that have shaped life on Earth for millions of years. A review in PMC notes that while flooding is widely seen as destructive, it also recharges groundwater, increases fish production, creates wildlife habitat, and rejuvenates soil fertility. These are not incidental benefits – they are integral to how many ecosystems function.

How floods sustain ecosystems and agriculture 🔗

Periodic flooding transports organic matter, minerals, and nutrient-rich sediments from upstream areas to downstream floodplains. This process maintains soil fertility and supports wetland ecosystems that many species rely on for breeding and feeding. Bangladesh offers a clear real-world example: the country experiences annual flooding that causes significant economic damage, but those same floodwaters carry nutrient-rich sediments from the Himalayas, effectively fertilizing agricultural land that sustains over 160 million people. Research published in the Philosophical Transactions of the Royal Society B highlights how soil’s role in regulating floods is deeply interconnected with soil fertility – floodplain soils downstream are often critically dependent on regular sediment inputs from upstream. When this natural cycle is interrupted, such as by large dams, the downstream fertility often declines.

How wildfires renew forests 🔗

Wildfires have a well-documented role in forest renewal. National Geographic explains that periodic fires clear accumulated dead organic material that would otherwise block soil organisms from accessing nutrients and prevent new plants from establishing. Burning also returns nutrients from dead plant and animal matter back into the soil much faster than slow decomposition would allow. Some species are so dependent on this process that they cannot reproduce without it – the Lodgepole pine, for instance, has cones covered in resin that only releases seeds when exposed to the high temperatures of a fire. Indigenous communities in Australia and North America recognized these benefits centuries before modern ecology did, using controlled burns to preserve landscape diversity and biodiversity.

Case studies: when hazards build rather than just destroy 🔗

Volcanic ash and soil fertility 🔗

One of the most striking examples of a hazard’s service function is the way volcanic ash rebuilds soil. Research from the Scripps Institution of Oceanography (UC San Diego) found that volcanic ash can triple plant productivity – not simply by acting as a mineral fertilizer, but by restructuring the soil microbiome itself. The ash stimulates beneficial bacteria and fungi, suppresses harmful soil parasites, and helps plants draw more nitrogen and other nutrients from the soil. This explains why volcanic regions around the world – from the slopes of Indonesia’s volcanoes to the Andes – are known for their exceptionally fertile soils.

A study examining volcanic ash from Indonesian eruptions found that while fresh ash disrupts agriculture in the short term, it secures soil fertility for future generations by supplying nutrients and building soil organic carbon stocks. The research describes volcanic ash as having a high capacity to sequester carbon from the atmosphere – a benefit that extends well beyond agriculture. A review in JSFA Reports further characterizes volcanic ash as a multi-nutrient mineral fertilizer that replenishes trace metals essential for soil bacterial activity and the cycling of key elements like nitrogen, carbon, phosphorus, and sulfur.

Mount St. Helens: a laboratory of renewal 🔗

When Mount St. Helens erupted in 1980, it devastated the surrounding landscape almost completely. Yet within years, the blast zone became one of the most closely studied examples of ecological recovery in science. Pioneer species – mosses, lichens, and nitrogen-fixing plants – colonized the ash-covered ground first, gradually rebuilding soil structure and organic matter. Today, the area supports a mosaic of habitats with greater biodiversity than existed before the eruption. The eruption demonstrated that volcanic disturbance, despite its severity, triggers a sequence of ecological succession that ultimately renews ecosystems rather than ending them.

Bangladesh floodplains: destruction and fertility in the same event 🔗

Bangladesh’s position in the delta of three major rivers means annual flooding is both a chronic hazard and an ecological cornerstone. The same floodwaters that displace communities and damage infrastructure carry Himalayan sediments that replenish the soil, support fish populations through expanded breeding habitat, and recharge wetlands. This tension – hazard and service function in the same event – is one of the clearest illustrations of why the concept of natural hazard “service functions” matters. Without understanding both sides, disaster management strategies can inadvertently destroy the ecological benefits while trying to eliminate the risks.

Why this distinction matters for hazard management 🔗

Recognizing the service functions of natural hazards does not mean accepting the deaths and economic damage they cause. It means designing smarter responses. The Millennium Ecosystem Assessment’s chapter on regulation of floods and fires makes the case that conserving natural ecosystems – floodplains, forests, wetlands – is itself a form of hazard regulation, because healthy ecosystems moderate the intensity of extreme events while preserving the ecological services those events provide. Flood management that works with natural sediment cycles, or fire management that allows low-intensity burns instead of total suppression, reflects this more complete understanding of how hazards function.

What do you think? If floods and wildfires provide genuine ecological benefits, how should this change the way governments and communities approach disaster prevention and land management? And given that volcanic ash can triple soil productivity over time, what ethical responsibilities do affected communities have in balancing immediate agricultural losses against long-term soil health?

References

1. https://www.intechopen.com/chapters/87034
2. https://www.ag-globalstrategies.com/natural-disaster
3. https://times.mw/understanding-the-layers-of-disaster-effects/
4. https://wiki.seg.org/wiki/Natural_disasters_and_hazards
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC6404734/
6. https://royalsocietypublishing.org/doi/10.1098/rstb.2020.0178
7. https://education.nationalgeographic.org/resource/ecological-benefits-fire/
8. https://scripps.ucsd.edu/news/volcanic-ash-supercharges-plant-growth-and-rebuilds-soil-life
9. https://www.mdpi.com/2071-1050/11/11/3072
10. https://scijournals.onlinelibrary.wiley.com/doi/10.1002/jsf2.87
11. https://www.millenniumassessment.org/documents/document.285.aspx.pdf