Many countriesrelyon tree planting to help reduce greenhouse gas emissions and meet future climate targets.

Nature and trees have been hailed as a “saviour” with a “mind-blowing” potential to tackle the climate crisis.

But there have also beenwarningsthat trees should not be solely seen as apermanentsolution for “carbon removal”.

Alongside removing carbon dioxide (CO2) from the air, forests provide a huge range of benefits for biodiversity and people around the world.

All these issues were discussed last week at the “Trees for Climate Change, Biodiversity and People” conference organised by theBritish Ecological Society.

Held at theUniversity of Kent, experts delved into tree diseases, woodland recovery and the future of forest landscapes.

Prof Yadvinder Malhi, professor of ecosystem science at theUniversity of Oxford, said the conference highlighted the “awe-inspiring” ways in which trees provide for nature, people and the environment.

Below, Carbon Brief summarises the key themes and issues discussed by scientists, researchers, practitioners and policy experts over the course of the two-day conference.

• How important are trees for climate change and biodiversity?
• What are the main threats to tree health?
• What benefits do trees provide for people?

How important are trees for climate change and biodiversity?

Trees are important for both climatemitigationandadaptation.

They absorb andstoreCO2 from the atmosphere and helpdefendagainst the intensity of some extreme weather events, such as heatwaves.

Prof Malhi tells Carbon Brief that trees are key for adapting to the effects of climate change, “particularly the restoration of trees and trees in城市周边and urban landscapes, where they can play an essential role in minimising the effects of peak temperatures or increased flood risk”.

Trees and woodlands can improve air quality, protect soils and host a range of biodiversity.

But trees can also be challenged by climate change. A 2019studyfound that climate change could cause trees to “live fast and die young”, reducing the ability of forests to act as acarbon sinkover long timescales.

Dr Cat Scottfrom theUniversity of Leedstold the conference that the UK’s land management practices are largely focused on what humans can get from the land in the form of products such as food and timber.

She said there is an “increasing realisation” that this has not led to ecologically diverse landscapes.

Scott is the director of theLeeds Ecosystem, Atmosphere and Forestcentre which helps manage four forest projects in northern England.

At these sites, researchers can monitor temperature changes in woodlands compared to open fields. During the record-toppingUK 2022 heatwave, Scott said temperatures were 15C lower in one project atHardknott Forestcompared to open grassland nearby.

Trees comprise a突出的部分of the UK’s plan to reach net-zero emissions by 2050. There are a number ofgovernmenttree-planting schemes and grants, including funding forfarmersto plant trees on their land.

But progress on tree planting has been “too slow”, according to the recentClimate Change Committee(CCC)reporton the UK government’sprogressin reducing emissions.

植树利率将到2025年必须翻一番reach the government’s target of 30,000 hectares of woodland creation per year, the CCC said.

The conference heard about the importance of having many different types of trees in a forest to ensure many different types of species can live there. For example, ash trees support 955 different species and oak supports 2,300.

Ross Barnettfrom theUniversity of Stirlingresearches how different landscape factors impact the complexity of sounds in a restored woodland.

This work explores whether woodland planted with just one type of tree supports significantly fewer invertebrates, pollinators and predators than woods with many tree varieties.

Dr Eleanor Tewfrom林业英格兰, England’s largest forest manager, said six tree species currently make up almost 70% of forest area managed by the organisation. Tew said the government agency is trying to increase the species diversity in its forests.

What are the main threats to tree health?

Alongside climate change and other threats facing trees in the UK and across the world, pests and diseases can have a major impact.

These diseases includeash diebackwhich is expected to kill up to 80% of the UK’s ash trees, according to the Woodland Trust.

Warmer temperatures and changing rainfall patterns have also led to increased tree mortality, according to theIntergovernmental Panel on Climate Change.

Dr Cecilia Dahlsjofrom theUniversity of Oxfordexplained that ash dieback is a fungal disease native to Asia. It has been present in the UK for more than a decade.

Dahlsjo described how ash dieback weakens a tree’s canopy, branches and trunk. It has a 70% mortality rate over a period of 10-15 years, she added.

Rebecca Gosling, conservation evidence officer for tree health at theWoodland Trust, told the conference that a new introduced pest or pathogen has been identified every 1.4 years in the UK. She said it is “quite a serious situation”.

Ash trees face another threat fromemerald ash borer, a beetle that has been “hitchhiking” into Europe from Russia and the US, Gosling said. This insect can cause significant damage to ash trees.

Prof Lucio Montecchiofrom theUniversity of Padovasaid that trade is the main way in which known and unknown plant parasites move between countries. He told the conference:

“Usually parasites [do] not move through wind from one country to another…fungi, bacteria, viruses – they must be moved.”

Quick response times are important, he said, alongside increasing local nurseries for trees and reducing imports from abroad.

Gosling told Carbon Brief that pests and diseases are “high up as one of the biggest threats our woods and trees have” in the UK. She said that experts fear climate change will “add another layer of threat” to trees:

“With climate change, the predictions are that our trees will become more stressed themselves. So, if they are suffering with more frequent droughts, as we’ve been seeing, the trees will be more stressed and, therefore, less able to defend themselves against a pest or pathogen.

“The second arm to that is that actually the pests themselves might find they’re more able to survive in the UK.”

Warming temperatures caused by climate change increase the risk that “more pests from warmer climates will be able to survive” in the UK, Gosling said.

In terms of current and future threats to UK forest landscapes, Malhi tells Carbon Brief:

“Pathogens are probably a bigger effect than climate change, and certainly bigger than deforestation and land use in terms of what’s going to shape these ecosystems over the coming decades.”

What benefits do trees provide for people?

A number of experts at the conference discussed research on the impact that trees can have on people.

佐伊·戴维斯教授from theUniversity of Kentresearches the “wellbeing benefits” people can get from being in nature.

She co-authored a study published inNature Sustainabilitywhich looked at the human wellbeing response to certain species traits, such as colour and sound.

The findings showed that many aspects of nature, such as bird song, can bring joy or other positive emotional responses.

Trees can also have cultural or local significance around the world.Dr Aliyu Salisu BaraufromBayero Universitydescribed how many neighbourhoods in Kano city, Nigeria are named after trees. They are important for local history, he told the conference, so tree loss can be a “disaster”.

People, especiallyIndigenous peoples and local communities, can often help to protect trees and forests. Astudyfound that Indigenous peoples played a “vital role” in the least-deforested areas of the Brazilian Amazon.

More than1.6bnpeople also rely on forests for timber, food, fuel, jobs and shelter.

Malhi said there should be greater research emphasis to show that “trees are more than just carbon” storage.

He told Carbon Brief that social science about nature highlights the “whole spectrum of values of trees” – ranging from ecological, cultural, spiritual and psychosocial. He added:

“There’s a whole frontier of research there about how people benefit from trees… I think much of the world, as the population gets more and more urban, is going through a nature deprivation catastrophe. I think that’s going to have lots of profound consequences for people’s wellbeing and welfare.”