How Climate Change Is Reshaping Our Forests

Forests have always felt steady and timeless, but the truth is, they’re changing faster than we realize. When you spend enough time in the woods, you start to notice things. Springs that used to be muddy are turning dusty. Summers feel hotter, the streams run lower, and some trees don’t look as healthy as they once did. Forests change slowly, but lately, the pace feels different.

In this article, we’ll explore 5 key ways climate change is reshaping our forests.

1. Drought and Water Stress

Trees can handle dry periods. They’ve survived millions of years of natural climate swings. However, heat now arrives earlier and lasts longer, rain is delayed, and the soil doesn’t easily bounce back. Instead of the occasional tough summers, many forests now move from one thirsty season to another with hardly a break.

drought-climate-change — *Source: United States Geological Survey (USGS)*

During dry periods, trees try to conserve moisture by tightening the stomata, tiny openings on the leaves that allow gas exchange. With those pores mostly shut, they can’t pull in enough carbon dioxide to fuel photosynthesis, so they start living off of the sugars and starches they’ve already stored. If the drought drags on and those reserves run out, the tree essentially starves (i.e. carbon starvation).

Drought stress also affects the tree’s plumbing system. As water becomes scarce, the tension inside the tree’s vessels increases, and pockets of air can form inside them. These air bubbles break the continuous water flow from roots to leaves. This failure is called hydraulic dysfunction. When this happens on a large scale, even a well-adapted tree can’t move enough water through its system and may die, not from lack of water directly, but from the collapse of its internal transport system.

Remote sensing studies have revealed clear pockets of drought-driven canopy decline across Europe, stretching from the Iberian Peninsula through France and Central Europe all the way to Finland. In some regions, including parts of Spain, France, and Eastern Europe, drought has accounted for roughly a third of canopy loss over the past 30 years. Between 1987–2016 alone, around 50,000 hectares experienced excess tree-crown mortality linked directly to water stress, and large percentage of the most intense drought events occurred in the 2000s and 2010s. The effects aren’t temporary, either; once drought weakens a forest, the consequences can continue to unfold for many years.

2. Wildfires

Fire has always played an important role in many forest ecosystems. In some cases, forest fires are even necessary, as for instance giant sequoias rely on heat to open their cones and release their seeds. In the boreal north occasional burns clear thick layers of organic matter so new trees can establish. It’s not the existence of fire that’s the problem, but its scale, timing, and intensity.

Wildfires are a major source of carbon dioxide emissions. In the period 2001–2023, global CO₂ emissions from forest fires increased by about 60%. This growth has been especially dramatic across the boreal regions of North America and Eurasia, where warming and drying trends fueled almost a threefold jump in emissions. The green expanses that circle the Arctic contain about 32% of global terrestiral carbon stocks. As the boreal forests burn hotter and more frequently, they are releasing massive amounts of carbon and accelerating atmospheric warming.

wildfire-climate-change — *Source: Pixabay*

Warmer temperatures, droughts, and stressed vegetation create forests that are more susceptible to ignition. Organic matter (leaves, needles, dead branches) dries faster than it once did, turning forest floors into fuel beds waiting for a spark. Nearly 85% of wildfires are still started by people, but climate sets the stage for how far and fast they spread. In the western United States, for example, climate-driven drying has helped double the number of large wildfires since the mid 1980s. A single degree of warming can dramatically expand the area burned in some western forest types, pushing fire seasons to last months longer than before.

3. Insects

Climate change is opening new doors for insects to invade forest in places they never operated before. After a drought or other stressful situation, the trees simply don’t have enough energy to defend themselves against these pests.

One of the most dramatic examples is the expansion and intensified impact of bark beetles. Although they play crucial roles in processes such as nutrient cycling and biodiversity, they are also servins as significant pests that can cause substantial economic losses. Bark beetles bore intricate tunnels just beneath the bark, where they feed and reproduce. These galleries sever the tree’s vascular system, eventually starving and killing the tree. Mild winters no longer kill of large insect populations and warmer summers allow more generations in a year. In western North America after about 2005, massive outbreaks of mountain pine beetles (Dendroctonus ponderosae) have killed millions of acres of forest from New Mexico to British Columbia.

In Europe, similar patterns are emerging. The spruce bark beetle (Ips typographus) is cutting deep into Central European spruce stands, with forest industries in countries like Czech Republic suffering price drops due to oversupply of damaged timber. In the period 2003–2016, bark beetles were damaging 0.2–1.4% of spruce growing stock in Czech forests annually, but in 2017–2019, this level increased to 3.1–5.4%.

bark-beetle-climate-change — *Source: Invasive.Org*

4. Fungal Pathogens

Fungal pathogens rarely act alone. Drought-stressed or insect-damaged trees are far more susceptible to infection, creating a feedback loop where climate stress, pests, and disease reinforce each other.

One of the most destructive examples in the northern hemisphere is Heterobasidion annosum, a root-rot fungus that attacks conifers such as spruce, fir, and pine. It spreads through root contact and airborne spores, slowly decaying the wood and making trees more vulnerable to windthrow. In Scandinavia and Central Europe, annual losses caused by this fungal pathogen are estimated at hundreds of millions of euros, and warmer winters are expected to extend its range northward.

heterobasidion-climate-change — *Source: Wikipedia*

Another well-known invader is Cryphonectria parasitica which causes a disease called chestnut blight. This disease wiped out the American chestnut in the early 20th century and now persists in Europe as well. In both continents, its spread has been accelerated by human movement of infected wood and by changing climates that favour its survival.

5. Extreme Weather

Storms, high winds, and floods. Natural disturbances are becoming stronger, more frequent and more unpredictable.

In 2018, a hurricane named “Vaia” hit northern Italy. SISEF (Italian Society of Silviculture and Forest Ecology) defined it as “an unprecedented phenomenon in the last 50 years”. Vaia brought wind speeds of up to 200 km/h and rainfall that surpassed even the catastrophic floods of 1966. Within hours, it uprooted an estimated 8.7 million cubic meters of forest, flattening more than 41,000 hectares of mountain woodland. To put in perspective, the same amount is harvested in an entire year of silvicultural activity in all Italy.

extreme-weather-climate-change — *Source: VAIA*

In the summer of 2021, Europe witnessed one of its most devastating flood events in modern history. In Germany’s valley of Ahr alone, over 150 mm of rain fell in just two days, washing away towns, roads, and damaging forests. Across Germany, Belgium and the Netherlands, the floods claimed hundreds of lives and left vast stretches of forestland damaged.

flood-climate-change — *Source: The New York Times*

What Can We Do?

It’s clear that simple actions like recycling or using fewer plastic bags are no longer enough. The effects of climate change are already unfolding. To protect forests and the ecosystems that depend on them, we must take bold, systematic action: drastically reduce fossil fuel use, restore degraded landscapes, and rethink land management on a global scale.

Of course, that’s easier said than done…