Endangerment and Extinction

Climate change is posing significant risks to the existence of trees, and in this highly industrial time, there is much human activity happening that is speeding up the cycle. It is important to be aware of the impact humans are making on tree populations, and wildlife populations that rely on forests and an abundance of trees.
Industrial activities are currently driving an unprecedented rate of forest loss, with estimates suggesting that up to 15 billion trees are cut down annually, while a chunk of forest the size of a football pitch is destroyed every two seconds.
Natural phenomena also contribute to the extinction of species, and we should not erroneously believe that humans are to blame for all of the climate concerns affecting trees!

Deforestation

The most direct cause of tree decline is the destruction of forests for agriculture, logging, mining, roads, and urban expansion. When forests are cleared, tree populations shrink immediately, and many species lose the specific habitats they need.
In a study carried out in the Amazon Rainforest, it was found that deforestation alone could cause 19–36% declines in tree species richness in parts of the Amazon by 2050 (Gomes et al., 2019).
Deforestation has a major impact on tree populations and the species that rely on them, as it removes mature seed-producing trees, destroys seedlings and soils, creates gaps in forests, and prevents pollination and seed dispersal. Furthermore, small, isolated human settlements that rely on trees for food or income will be greatly affected!

The climate crisis is widely discussed in society, but how exactly does it affect trees? Rising temperatures, shifting rainfall, droughts, heatwaves, storms, and altered seasons can exceed what tree species are able to tolerate. Trees are long-lived organisms that have adapted to suit one climate, and when it changes, they are unable to adapt quickly enough to save themselves.
Sadly, wildfires and bushfires have become normal, expected occurences in hot areas such as California and Australia, respectively.
During droughts, hydraulic failure can occur when trees are unable to transport enough water from roots to their leaves, causing them to die from within.
Heat damages photosynthesis - the stomata will close at very high temperatures, reducing the intake of carbon dioxide.
Climate change alone could cause 31–37% declines in species richness, potentially overtaking deforestation as the biggest threat in the coming decades. (Gomes et al., 2019)
The expected future climate with increasing drought episodes, seasonally warm temperatures, and severe storms, poses a challenge for forest management since it will affect the growth, mortality, species composition, and distribution of future forests (Huang et al., 2024). However, the topic of how growth is affected by climate change is currently poorly understood.

Even when forests are not completely destroyed, roads, farms, and development can split them into smaller patches, in which trees often cannot survive in the long term.
Fragmentation reduces gene flow between trees and limits the biodiversity of the forest, making it more susceptible to invasive species (Boonman et al., 2024). It also means that there are fewer other trees to cross-pollinate with, resulting in depopulation of that species. Trees may "inbreed" - mate with themselves or closely related individuals - resulting in reduced genetic diversity, deformities, and a higher mortality rate. Although a natural phenomenon, it is far more prevalent in fragmented forests.

Trees can be impacted by fungi, insects, bacteria, and pathogens that are not native to the area - they can devastate tree species that evolved without defences against them.
Research on the European Ash showed that invasive pathogens could severely impact the population of the species - their model predicted that Ash Dieback (a pathogen) could reduce the Ash population by around 26% in 10 years. (Wu et al., 2024)
Infestation of invasive species means that regions may face "local extinction" of particular tree species - it is important to monitor pests to ensure that trees are not affected.

Fungus on a tree trunk - a common sight in many forests.

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