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A single street tree can potentially increase an average Sydney house price by A$30,000, our new research shows. This echoes past research showing street trees not only help boost property prices, but offer other benefits, from improved scenery and privacy to increased shade.

But there's a catch. Our analysis, published in the international Cities journal, also found that if a street tree is too close, it can actually reduce the selling price by more than $70,000.

Our study looked at more than 1,500 house sales in the City of Sydney from 2021 to 2024, then matched those with detailed council data on nearly 50,000 public trees.

After accounting for other, better known price factors - number of bedrooms, bathrooms, car parking, land size, proximity to the CBD, transport, schools and more - we found trees can be associated with higher house prices. But that price boost only occurred when the trees were about 10-20 metres from a home, such as across the street or near the frontage.

In contrast, trees planted too close - within a 10m radius from the centre of the property - were actually associated with lower sale prices.

This matters beyond Sydney. Every Australian capital city has set tree-planting goals, such as the City of Sydney's target for 23% tree canopy cover in 2030 and 27% in 2050. Yet many will struggle to meet them, with some facing resistance from residents. Our research explains why tree placement will be crucial if we ever want to meet those targets.

Past studies in Perth, as well as several cities in the United States and Canada, have consistently shown trees tend to increase property values.

But what we didn't know before now was where the benefits stop and the costs begin.

Our study identifies a clear "not in my backyard" (NIMBY) boundary, of around 10m, within which street trees' economic value turns negative.

That finding is important, because that's when resident resistance to street trees is likely to be strongest.

This is a first study of its kind to quantify the economic value of public trees by taking advantage of using individual tree-level data managed by the City of Sydney from 2023.

It allowed us to measure tree effects at the finest possible distance from the centre of property: under 10m, 10-20m, 20-50m, 50-100m, and beyond 100m. This is something previous studies could not do when relying on satellite or street imagery.

We controlled for all the usual factors that influence house prices, including property features and location amenities. This meant we could measure the impact of trees after accounting for everything else.

We found that distance matters. In dollar terms, one additional tree within 10m of the centre of a property reduced its value by 2.96%. An average home sold in the City of Sydney from 2021 to 2024 was worth $2,613,000 - so that reduction worked out to be a $70,290 cost.

Given the average lot size of 176m in the City of Sydney, the distance from the centre of an average property to its boundary is typically about 8m.

But if a tree was located 10-20 metres away, it increased the value by about 1.16%, worth an average of $30,310.

If the tree was further than 20 metres away, we found no price difference.

This show a clear proximity effect. Trees being too close to a house are a cost risk; trees at a moderate distance are a valued feature; and trees further away are neutral and just part of the neighbourhood amenity.

Our study used more precise data than ever before to calculate the distance between street trees and the centre of each property.

But future research could take this further by measuring the distance from each tree to the house. It could also incorporate resident surveys to better understand how people perceive and value trees near their homes.

It makes sense that people may see trees close to home as a financial risk.

Trees can cause structural damage to buildings and infrastructure, increase fire hazards, and safety concerns from falling branches.

Rather than dismissing residents' concerns as NIMBYism, they should be seen as rational market responses to maintenance risks, structural damage, and amenity loss.

Every Australian capital city has adopted "urban forest" or tree planting strategies, many of them aiming to hit 30-40% canopy cover in coming decades. For example, the City of Melbourne's target is 40% canopy cover by 2040, while Brisbane City Council is aiming for 50% shade for residential footpaths and bikeways by 2031.

However, there are doubts about whether many of those targets will be met.

There are good reasons for governments to invest in urban trees, as they can protect us from extreme heat and help as a response to climate change. But resistance from homeowners can undermine these policies.

Our research shows residents are more likely to welcome street trees if they're planted not too close, and not too far, from their homes.

* Thanks to the coauthors of this paper, Qiulin Ke and Bin Chi from University College London.