It may feel counter-intuitive to discuss heat stress as the nights are starting to turn colder, but the climate change data is unambiguous: hotter, drier summers and shorter, more intense downpours are here to stay.
With this in mind, Forestry England recently released a new ‘species for the future’ list of trees most likely to thrive in our climate as the world warms up, including native trees such as oak, hornbeam and beech, alongside others such as the Corsican pine or Japanese red cedar.
It’s not just a consideration for creating climate-change-resilient rural habitats, though; street trees are particularly vulnerable to this new-normal weather pattern. Extended dry spells starve shallow root systems, while sudden storms overwhelm compacted sub-bases and oxygen-poor soils.
However, we’d suggest that tree choice is only part of a successful strategy to ensure climate change resilience. If your response is limited to swapping in ‘resilient species’, you may buy a few seasons – but not decades. In the built environment, longevity is engineered below ground or not at all.
The limits of the planting list
‘Pick tougher species’ is a neat, headline-worthy message that reassures people that the solution is straightforward – just choose the right trees and everything will be fine. But this soundbite drowns out another significant limiting factor in tree health and resilience, which is also the real opportunity: the below-ground environment.
Where soil volume is inadequate, continuity is broken, and air/water movement is blocked, even the most tolerant species under-perform. The symptoms are familiar – stunted growth, canopy dieback, recurring replacement cycles – and they are expensive. If your specification cannot answer these three basic questions, then it suggests species choice is a cosmetic decision, not a resilience strategy, and a more holistic approach is needed:
- How much functioning soil is there per tree?
- How does water reach and leave the root zone?
- How is oxygen exchange maintained?
Tree pits as infrastructure
The alternative approach is straightforward and gets far more dependable results – design tree pits as active infrastructure. Provide continuous, structural rooting volume beneath pavements so loads are carried without settlement and roots can explore. Accept roof and pavement runoff through protected inlets; filter silt before it enters the system; and move water through an engineered soil profile that stores, cleans and slowly releases it. Build in aeration and inspection points so performance can be verified and maintained, not assumed. During a storm, flows are attenuated and routed; between events, stored moisture is available to the roots.
This is not ‘landscaping’, it is distributed climate adaptation engineered to reduce peak flows, improve thermal comfort and grow trees to maturity.
None of this removes the need for intelligent species selection, of course, it simply reframes it as a part of the solution. Tree selection should be driven by the microclimate of the area in question (street orientation, canyon effect, radiant load and salt exposure all have a bearing) and the conditions you expect in two decades, not last decade’s averages. Provenance and biosecurity also need to be borne in mind, so does operational reality (crown spread, litter, allergen management, pruning regimes). It’s also worth remembering that diversity is a useful risk-management tool; mixing species and genera means that one pest, pathogen or climatic quirk cannot take out an entire streetscape.
But it’s worth remembering the relationship between these important aspects – the below-ground design is the foundation, the species list is the optimisation layer.
Design with heat and water in mind
Urban heat islands are a key consideration. Dark, heat-absorbing surfaces and narrow, tall-sided streets amplify heat at pedestrian level, precisely where shade and evapotranspiration are most valuable for street trees, so specifications should reflect that reality:
- Right-size the soil volume per tree and protect it structurally; provide defined routes for air and water; and favour passive irrigation as a default.
- Surface choices also matter, with lighter, permeable finishes reducing radiant load and improving infiltration.
- Protection measures must be growth-tolerant and maintenance-practical; guards and grates that cause constrictions create new problems just as fast as they solve old ones.
A single well-designed pit is helpful for urban tree health, but a connected sequence can be transformative for a street or square. When pits are networked – linked to raingardens, planters and sub-surface storage – they function as a distributed sponge. Peak flows are mitigated during intense rainfall, water quality improves through biofiltration, and moisture is retained in the root zone for longer between events. The drainage network benefits and so do the trees. This is where the often-separate conversations about SuDS and urban tree health converge: it’s one system with dual benefits. Flood mitigation and canopy performance are the two birds, green-blue infrastructure the one well-designed stone.
It’s also worth bearing in mind that every late design change costs more than an early decision – so bringing highways, drainage, landscape architecture, planning and maintenance functions together at the start is a wise choice. That way, you can lock in rooting volume before kerbs and utilities are frozen, and decide flow paths and overflows before the gullies are placed. These are not soft-skills meetings; they are the moments where collaboration results in the most efficient and effective design on all fronts.
Manage as assets, not decorations
Planting day is the start of the process, not the objective itself – ongoing optimal performance is a key consideration for success long term. Maintenance isn’t onerous, but it does need to be borne in mind at design stage; inspection ports enable silt checks, infiltration measurements and irrigation verification.
Routine tasks – clearing inlets, confirming aeration, recording crown growth – need to become part of an asset plan (as outlined in the new SuDS Standards) rather than a retroactive scramble when something fails. Over time, reporting survival rates, growth trajectories and infiltration volumes against maintenance inputs will provide data that defends budgets and accelerates approvals for future schemes, because you are no longer asking stakeholders to take the benefits on faith.
The business case for climate-resilient trees
A resilience-improving network of thoughtfully designed tree pits replaces recurring replacement cycles and reactive callouts with predictable growth, measurable cooling and quantifiable peak-flow reduction. In practice, that means lower lifecycle cost, fewer reputational hits from failing streetscapes, and a stronger planning position on subsequent schemes. When you treat trees as climate infrastructure – carefully engineered, connected, inspected – you don’t just get healthier canopies, you get a system that pays its way in reduced flood risk, improved comfort and simpler operations.
“Plant tougher trees” is not a strategy, it’s a part of a complex, engineered problem-solving solution. The truly climate-resilient outcome pairs right-sized, connected, verifiable tree pits with species and provenance choices that fit the microclimate of the urban area in question.
If you want to de-risk a live or upcoming scheme, start with the drawings: soil volume, air/water routes, SuDS connectivity, inspection points. We can help. Just submit your plans to us and we can offer a specification review that helps you take a strategic approach to urban tree climate resilience.
