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Seedling Mortality: Understanding the Causes and Mitigating the Risks

  • Writer: Leaf.it
    Leaf.it
  • Apr 1
  • 5 min read

As organizations increasingly invest in reforestation and urban greening initiatives, seedling survival becomes a critical success factor. Alarmingly, a significant proportion of planted seedlings never reach maturity - a challenge with serious implications for carbon offsetting, biodiversity, and long-term ecosystem harmony. Understanding the drivers behind seedling mortality is essential to improving survival rates, ensuring return on investment of tree planting, and achieving meaningful environmental outcomes. Read on to learn more from our comprehensive research inisghts article about the causes of seedling mortality and our approach to solve this problem!


Why Seedling Mortality Matters

Seedlings form the foundation of future forests and urban green infrastructure. When mortality rates are high, the result is a loss of ecological services such as carbon sequestration, air purification, and urban cooling (6). Moreover, the financial and labor costs associated with tree planting efforts become highly inefficient when survival rates are not adequately tracked or supported post-planting (4, 5). This makes reducing mortality not only an ecological priority, but also a strategic necessity for both urban and forestry purposes.


Exploring the Causes of Seedling Mortality

 

The main causes:

  • Environmental Stressors

  • Biotic Stressors

  • Infrastructure and Maintenance

  • Poorly executed planting processes

  • Post-planting monitoring and management

 

Environmental Stressors: Drought, Soil, and Climate Conditions


Environmental stress is one of the leading causes of seedling mortality. Drought in particular significantly limits seedling establishment, especially in areas that are increasingly impacted by climate change (14).

Young trees have shallow root systems and limited capacity to withstand prolonged water deficits (17). Urban environments introduce additional challenges: compacted or contaminated soils, high surface temperatures due to impervious cover, and limited rooting space all contribute to lower survival rates (1, 2).

In poorly drained or nutrient-deficient soils, seedlings struggle to compete with existing vegetation (13). The growing frequency of extreme weather events, such as forest fires, floods, drought and heavy storms, further complicates efforts to ensure successful survival of younger trees (17).




Biotic Stress: Animals and Pathogens

Bark beetle dangered areas in Germany

Biotic factors such as herbivory (foe example, by deer, rodents, or insects) and pathogens are another major cause of early seedling mortality (11). In natural systems, these pressures can help maintain species diversity (11, 12).

On the other hand, in reforestation efforts and urban contexts, they represent a considerable risk to young plantings. For example, bark beetles represent a significant danger for needle trees in Germany, demonstrated by map on the left. Without adequate protective measures, seedlings are highly vulnerable to browsing damage or diseases, particularly when already weakened by environmental stressors (3).


Urban Challenges: Infrastructure and Maintenance Gaps

Urban seedlings face unique pressures. Beyond environmental and biological stress, city-planted trees often contend with root space limitations, air and soil pollution, and human interference (2). Additionally, many municipalities or private developers lack the resources or planning frameworks to provide adequate post-planting maintenance during the critical establishment period.

Research, however, consistently shows that tree performance in urban settings improves significantly with consistent care and infrastructure planning that prioritizes green space resilience (1, 2, 3), providing hope for all involved parties in the success of tree planting efforts.

Urban tree planting faces different challenges when it comes to seedling mortality

Nursery and Planting Practices

Seedlng mortality can be reduced by adequate planting practices
Adaquate planting processes are crucial for seedlings to reach maturity

The quality of nursery-grown stock plays a key role in seedling survival. Poorly developed root systems, inadequate hardening-off, or planting outside the optimal season can all increase mortality risk (8, 15). Stress encountered during the production phase can result in seedlings that are ill-equipped to transition to field conditions (16).

Conversely, seedlings grown under optimal nursery conditions - with attention to root structure, hardiness, and site-specific adaptations - demonstrate markedly better survival and growth (7, 16).


Lack of Monitoring and Adaptive Management

One of the most overlooked factors in seedling mortality is the absence of effective post-planting monitoring. Many large-scale initiatives report success based on the number of trees planted rather than those that survive and thrive (4, 18). Without follow-up, adaptive management, or scheduled replacement strategies, early losses can go unnoticed - eroding the long-term impact of tree planting investments.



The Solution

Seedling mortality is not an inevitable cost of planting - it is a solvable challenge. By understanding its causes and incorporating science-based strategies into planting and management workflows, organizations can significantly improve tree survival rates.


Whether the goal is carbon sequestration, biodiversity restoration, or urban resilience, the long-term success of tree planting projects depends not on how many trees go into the ground - but how many grow into the canopy.


Leaf.it’s seedling protection product is designed specifically to address these challenges. By shielding young trees from environmental stressors, herbivory, and human interference, our solution plays a critical role in improving survival rates and maximizing the impact of every planting effort. It’s an investment not only in tree protection - but in the long-term success of your sustainability goals.


Read more about our tree planting insights at the next post!


Promote reforestation be reducing seedling mortality!


References

  1. Nowak, D.J., & Greenfield, E.J. (2012). "Tree and impervious cover change in U.S. cities." Urban Forestry & Urban Greening, 11(1), 21-30. 

  2. McPherson, G., et al. (2016). "Urban tree performance & maintenance in North America." Ecological Applications, 26(7), 2315-2332.

  3. Roman, L.A., et al. (2014). "Urban tree mortality: a literature review." Arboriculture & Urban Forestry, 40(5), 189-202.

  4. Conway, T.M., & Urbani, L. (2007). "Variability in urban tree mortality rates and implications for tree replacement." Urban Forestry & Urban Greening, 6(4), 181-190.

  5. Nowak, D.J., & Dwyer, J.F. (2007). "Understanding the benefits and costs of urban forest ecosystems." Urban and Community Forestry in the Northeast, 25(4), 25-46.

  6. Grote, R., et al. (2016). "Urban trees and air quality." Environmental Pollution, 216, 482-491.

  7. Grossnickle, S.C. (2000). "Ecophysiology of northern spruce species: The performance of planted seedlings." NRC Research Press.

  8. Landis, T.D. (2013). "Seedling quality and reforestation success." USDA Forest Service Proceedings, RMRS-P-68.

  9. Fenner, M. (1987). "Seedlings" New Phytologist, 106(S1), 35-47.

  10. Wellington, A.B., & Noble, I.R. (1985). "Seedling mortality due to drought and grazing in Eucalyptus woodlands." Australian Journal of Ecology, 10(1), 117-125.

  11. Janzen, D.H. (1970). "Herbivores and the number of tree species in tropical forests." The American Naturalist, 104(940), 501-528.

  12. Connell, J.H. (1971). "On the role of natural enemies in preventing competitive exclusion in some marine animals and in rain forest trees." Dynamics of Populations, 298-312.

  13. Keizer, P.J., et al. (1985). "Seedling establishment and vegetation interactions in nutrient-poor soils." Oecologia, 68(4), 545-550.

  14. Bréda, N., et al. (2006). "Forest tree responses to drought: What have we learned?" Tree Physiology, 26(4), 389-403.

  15. Davis, A.S., et al. (2011). "Nursery practices influence seedling stress resistance and field performance." Tree Physiology, 31(6), 569-579.

  16. ​Pawłowski et al., D. J. (2024). Climate legacy in seed and seedling traits of European beech populations

  17. European State Forest Association AISBL. (2020). Forest dieback/damages in European State Forests and measures to combat it. https://eustafor.eu/uploads/Forest-dieback-in-Europe-and-measures-to-combat-it_aug.pdf

  18. Projects monitoring in Europe: a rigorous process for assessing the health of restored ecosystems. (2024, June 4). Reforest’Action. https://www.reforestaction.com/en/magazine/monitoring-projects-europe-2023

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