Ecological Succession: Definition, Types, Process, Stages and Impacts

Context: Climate change is increasingly disrupting natural patterns of ecological succession in India’s fragile ecosystems, demanding restoration strategies that build resilience against rising temperatures, altered rainfall, and invasive species.

What is Ecological Succession?

Ecological succession is the gradual and natural transformation of ecosystems over time, through predictable changes in species composition and community structure. There are two main types:

• Primary Succession happens in lifeless areas, like lava flows or new dunes, where soil cannot support life.
• Secondary Succession occurs in areas where an existing community has been disturbed, but some life and nutrients remain, like after a fire or flood.

In Secondary Succession, the process starts in places with soil, and it can also happen in abandoned farmland, known as old-field succession. Both types lead to changes in species as the environment evolves. Initially, only a few species can survive, but as new plants grow, they change the habitat, allowing different species to thrive. This pattern continues, with plants and animals influencing each other and the environment as they change over time.

Process of Ecological Succession

It is the process of evolution of a species in a steady and gradual manner in a region over a period of time. It can also be described as the way species move into and take over an empty area in an ecosystem. This process shows how species change and develop over a long time, starting from:

Pioneer Species –> Intermediate Species –> Climax Species

• Begins with pioneer species (lichens, mosses) colonising barren areas.
• Proceeds through intermediate (seral) stages, with increasing complexity.
• Ends with a climax community — stable, self-sustaining ecosystems dominated by long-lived species.

Significance: Provides resilience to ecosystems, enabling recovery after natural disasters (floods, volcanic eruptions) and human disturbances (logging, deforestation).

Types of Ecological Succession

There are two main types of Ecological Succession: Primary Succession & Secondary Succession.

Primary Succession

It thrives in areas with no plants and poor soil, like dunes, bare ocean surfaces, new deltas, lava flows, and emerging volcanic islands. The process starts with microorganisms and plants like lichens and mosses. When these pioneers die and decay, they release nutrients into the soil, making the area better for new plants like grasses, shrubs, and sun-loving trees like pines. Over time, this leads to a stable community with shade-tolerant trees like oaks.

Secondary Succession

It happens when a mature or growing community is damaged or destroyed by natural events like floods, droughts, forest fires, or storms, or by human activities like deforestation, farming, and overgrazing. As some of the sediments from the previous community are already present, the development of the secondary succession is relatively faster than the primary community. And with the passage of time forest community develops.

Stages of Ecological Succession

The mixing of species and habitat during the process of ecological succession goes through 5 stages:

Causes of Ecological Succession

Initial Causes: They cause damage to existing habitats. This can happen because of:

• Climatic Factors: Things like wind, fire, erosion, and natural disasters.
• Biotic Factors: This includes competition between living things for survival.

Continuous Causes: It is also known as ecesis. This process involves competition, movement of species, and gathering together. It leads to changes in the soil, such as changes in soil pH, buildup of organic matter, and changes in nutrients.

Ecological Succession in an Ecosystem

Ecological succession is essential for the healthy growth and development of the ecosystem as it initiates the colonisation and diversification of a new region and the recolonisation of a region that has been wiped out due to natural and anthropogenic causes.

Ecological Succession and Stability of Ecosystem: Succession occurs in a series of stages which lead to the establishment of a stable and final community. The final stable community of plants is called the Climax community.

Ecological Succession and Diversity in Ecosystem: Ecological Succession provides diversity as well as depth to a biotic community in an ecosystem. Succession is the gateway of evolution, without which life cannot grow or progress.

Ecological Succession Helps Maintain Equilibrium in an Ecosystem:  A community goes through stages of ecological succession until it reaches equilibrium. When a community reaches the climax stage of succession, the composition of the community becomes stable; thus, any small changes or disturbances will be counterbalanced by other changes to restore the original stage.

How Climate Change is Disrupting Succession

• Frequent Disturbances: Repeated fires, floods, and storms “reset” succession, preventing ecosystems from reaching climax stages.
• Phenological Shifts: Flowering and pollination timings no longer align, weakening regeneration.
• Soil and Water Stress: Altered rainfall, salinity, and temperature hinder native species’ survival.
• Invasive Species: Disturbed habitats are colonised by hardy invasives (Lantana camara, Acacia spp., Pteridium aquilinum), which block natural regeneration.
• Impact: Loss of biodiversity, carbon storage, and ecosystem resilience.

Impact on India’s major Biogeographic Zones

Ecological Succession in the Himalayas

• Treeline shifts: Due to rising temperatures, the upper boundary where trees can grow (treeline) is moving higher up the mountains.
• Decline of oaks: Banj oak (Quercus leucotrichophora), a late-successional and stable forest species, is struggling to regenerate because of human pressures (grazing, logging) and frequent fires.
• Pine expansion: Instead of oaks, early-stage species like chir pine and grasses, which tolerate stress, are spreading.
• Species migration: High-altitude species like Abies spectabilis (East Himalayan fir), Rhododendron campanulatum, and Betula utilis (Himalayan birch) are shifting further upslope.
• Impact:
  • Hardwoods (oak, birch) that support rich biodiversity are declining.
  • Loss of habitat for many birds and mammals.
  • Changes in migration and feeding patterns of Himalayan fauna.

Ecological Succession in the Sundarbans

• Salinity stress: Sea-level rise and reduced rainfall are making soils more saline.
• Normal succession: Salt-tolerant pioneers (Avicennia officinalis) usually pave the way for less salt-tolerant climax mangroves like Heritiera fomes (sundari).
• Disruption now: High salinity favours pioneers, but sundari trees are declining.
• Impact:
  • Mangrove forests lose resilience against cyclones.
  • Biomass and carbon storage decrease.
  • Fish, prawns, and crabs that depend on diverse mangroves lose breeding grounds.

Ecological Succession in the Western Ghats

• Fire frequency rising: Fires used to maintain a balance between grasslands and forests. But now, repeated fires prevent forests from maturing.
• Blocked regeneration: Seedlings of late-successional hardwood trees die in every fire, so climax forests cannot form.
• Invasive takeover: Disturbed landscapes are quickly colonised by invasive species like Lantana camara, Acacia (wattle), and Pteridium aquilinum (fern).
• Impact:
  • Native forests are replaced by invasive-dominated scrublands.
  • Less food for wild herbivores like elephants and gaur.
  • Soil fertility and water-holding capacity decline.
  • Long-term ecosystem degradation.

Way Forward: Tackling Climate-Driven Disruptions in Ecological Succession

• Succession-Informed Restoration: Restore ecosystems along natural successional pathways, not by planting fast-growing monocultures.
  • Use native, climate-tolerant species suited to local conditions and seral stages.
• Promote Passive Recovery: Allow ecosystems to regenerate naturally where possible. Use active restoration only in severely degraded or high-risk sites.
• Manage Invasive Species and Disturbances: Control invasives like Lantana and Acacia through fire and grazing management. Prevent repeated resets of ecosystems to early stages.
• Climate-Resilient Planning: Anticipate treeline shifts, salinity rise, and rainfall changes. Use assisted migration for vulnerable climax species (e.g., Himalayan oak, Sundarbans’ sundari).
• Phenology-Aligned Actions: Time restoration with local flowering, pollination, and seed dispersal cycles to avoid mismatches.
• Landscape and Watershed Approaches: Restore forests, wetlands, rivers, and grasslands in an integrated way to maintain soil, water, and connectivity.
• Monitoring and Early Warning: Use satellites, drones, and AI to track succession stages, invasive spread, and treeline shifts for adaptive management.
• Community-Based Conservation: Empower local and tribal communities to manage fires, grazing, and invasives.
  • Link livelihoods with conservation (eco-tourism, mangrove fisheries, agroforestry).
• Policy Reorientation: Shift from carbon-focused afforestation to ecosystem-centric restoration. Integrate ecological succession into forest, coastal, and biodiversity policies.

Ecological succession is the engine of ecosystem development and resilience, yet climate change and human disturbances are derailing natural pathways in fragile regions. India’s conservation strategies must therefore move beyond tree planting to ecologically informed restoration that respects native species, natural stages of succession, and local contexts.

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