Not as reliably as they once were. A four-decade analysis of Swiss protective forests found that higher elevation remained associated with lower drought-stress metrics, but the resilience advantage of growing stands at higher altitudes progressively faded. The finding concerns how forests withstand and recover from drought—not proof that altitude no longer matters or that every mountain forest now responds like a lowland one.
What the study found about altitude and drought
Estelle Noyer, Luuk Dorren, Barbara Allgaier Leuch, and Christine Moos analyzed Swiss National Forest Inventory data from 1983–2022 alongside satellite observations of canopy moisture. Their study, published in Frontiers in Forests and Global Change on 1 October 2026, found a changing relationship between elevation and the resilience of growing stands.
The distinction is important: drought stress and drought resilience are related, but they are not the same measure. Across inventory periods, drought-stress metrics generally decreased with altitude. Yet among stands classified as growing, the altitude effect on canopy resilience weakened over time. Combined resilience lost its altitude relationship first, followed by resistance; the relationship with recovery disappeared in the most recent period. The authors interpret this pattern as a convergence in canopy responses across elevations.
That does not establish that high elevations have lost every advantage against drought. Nor does it show that elevation has no bearing on other forest conditions. It shows that, in the growing stands and resilience measures studied, higher altitude became a less reliable predictor of how the canopy resisted and recovered from drought.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
#1 Best Overall
- Convenient Size: Measures approximately 5.5 x 8.3 inches, offering ample space for writing while remaining small enough to fit into most bags, making it practical for home, study, or travel use.
- Sturdy Hardcover: The firm cover helps maintain structure and protects pages from damage, ensuring your notes remain tidy in both stationary and mobile settings.
- Suitable for Gifting: With its clean, functional style, it works well as a gift for colleagues, learners, or anyone who enjoys writing, planning, or organizing.
- Smooth Writing Surface: Inner pages provide a uniform, clear surface for writing, great for note-taking, journaling, or planning without interference from texture or shine.
- Flexible Use: Spiral binding lets the notebook lie flat or fold back completely, allowing comfortable writing in tight spaces or with one hand.
Stress, resistance, recovery and resilience: what the terms mean
- Drought stress describes the drought conditions or impacts reflected in the study’s metrics. These generally remained lower at higher elevations.
- Resistance captures how well canopy moisture holds up during a drought.
- Recovery captures the canopy’s response after drought.
- Combined resilience brings resistance and recovery together to describe canopy response across the drought episode.
The researchers estimated canopy moisture using the Normalized Difference Moisture Index (NDMI), calculated from August Landsat images. NDMI is an indicator of canopy moisture; it is not a direct measurement of tree growth or biomass.
How the Swiss forest analysis was conducted
The researchers retained an average of 1,380 protective-forest stands per inventory period, with a range of 891–1,543. The plots spanned 281.9 to 2,218.6 metres above sea level and were grouped into five elevation belts. Plots showing recent forestry intervention or fire traces were excluded.
For stand structure, the team examined measures including basal area and net stem density. For canopy moisture, it used Landsat 5, 7 and 8 observations from August 1984–2022. Each inventory-period analysis was conducted separately, so this is an observational account of patterns over time—not a randomized experiment that proves what caused them.
Rank #2
- STORE PRACTICAL INFO & MEMORIES OF YOUR CAMPING TRIPS: Clever Fox Camping Notebook is designed to help you prepare for your camping trips, store helpful information about the campsites you visit, and preserve your favorite memories from your travels.
- CAMP NOTES & SPACE FOR MEMORIES: You can record up to 14 camping trips in this travel log book. Each trip entry has a detailed camp overview, arrival and site notes, and 3 dotted pages to add memories, photos, or customize however you like.
- COMES WITH STICKERS & STORAGE POCKET: This traveling journal comes with 3 sheets of stickers to decorate the pages. At the back, you will find an expandable pocket, where you can store maps, business cards, photos, and other loose papers.
- POCKET SIZE & DURABLE MATERIALS: This travel log book journal comes in a pocket size (3.7x5.7”), perfect for on-the-go use. The RV travel journal has an eco-leather hardcover, thick 120gsm paper, pen loop, elastic band, and bookmark.
- 60-DAY MONEY-BACK GUARANTEE: We will exchange or refund your adventure book if you aren’t satisfied with your camping essentials for women and men for any reason. Reach out to us via message to refund your camping accessories for rv campers.
Stands with positive relative basal-area increment were classed as “growing”; those with negative increment were classed as “declining.” The distinction matters because the two groups showed different patterns.
The Tool Desk
Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Growing and declining stands showed different patterns
| Stand group | What the study found |
|---|---|
| Growing | The altitude effect on drought resilience progressively faded: first for combined resilience, then resistance, and finally recovery in the latest period. Average relative annual net stem-density increment fell from 2.84% in the first inventory interval to 1.92% in the last. |
| Declining | Drought stress was higher, particularly in the two most recent inventory periods. The researchers found no altitude-related differences in the resilience components in any period. |
In growing stands, the overall decline in basal-area increment was driven by falling stem density, rather than reduced average growth by individual trees, according to the authors. Net stem-density change cannot, however, distinguish tree mortality from new trees entering the measured population.
Why high-elevation forests are not immune
Five extreme drought episodes—2003, 2006, 2015, 2018 and 2022—each affected more than 30% of the studied stands, including stands in the highest elevation belt. That finding shows that severe drought reached stands across the elevation range; it does not mean every stand was affected equally.
The study also found broad drought vulnerability among large, dominant trees. In declining stands in the highest belt, growth shifted toward smaller trees in the two latest periods. The authors say it remains unclear whether that pattern signals a route to recovery or a slower decline.
Why the results matter for protective forests
Protective forests are managed for their role in helping shield people and infrastructure from hazards such as avalanches, rockfall, landslides, flooding, and debris or sediment transport. The study’s introduction, citing Strauss and Fischer (2025), reports that they cover 540,000 hectares—44% of Switzerland’s forest area.
Free tools Windows power users keep installed
One-click scans. No signup required.
If stands become less able to withstand or recover from drought, their protective function may be at greater risk. In an interview with Earth.com, lead author Estelle Noyer said the findings suggest protective forests could offer less protection against natural hazards, particularly at lower elevations. That is a practical concern, not a measured forecast of specific damage to any town or infrastructure.
Rank #4
- UNIQUE. Each image is hand-drawn by skilled artist Kathryn Marlin!
- PREMIUM QUALITY PAPER. Single-side printed on 90 lb. Acid-Free Smooth Index SFI certified paper.
- DURABLE AND RIGID. No desk required. Constructed with a sturdy 100% recycled chipboard back, a firm yet flexible clear cover, and bound with WIRE-Oô double loop binding for a true LAY-FLAT experience.
- USE MARKERS WORRY FREE! Includes a movable poly sheet which prevents colors from bleeding through to other pages.
- MADE IN USA! Our products are designed and produced by people who care about you and our planet.
What the study suggests—and does not prove—about management
The authors point to adaptive management that preserves sufficient stem density, structural heterogeneity and cohorts of drought-tolerant trees. These are proposed priorities, not treatments whose effectiveness this study tested. It does not quantify how much thinning, a particular species mix, or any other intervention would reduce drought risk, and it does not prescribe a universal planting recipe.
The authors describe the greatest need for attention at low and middle elevations, while the findings also show that extreme drought affected stands in the highest belt. Management decisions therefore need to reflect local forest conditions and hazard-protection needs rather than assume that elevation alone ensures resilience.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to interpret the evidence
The analysis documents long-term patterns; it does not demonstrate that climate change alone caused every change. The authors discuss repeated drought, changes in forest composition and acclimation as possible contributors. The study did not include tree species as a predictor, so it cannot determine whether patterns reflect differences among trees of the same species or turnover toward more drought-tolerant species.
There are also measurement limits. The water-balance drought index does not represent delayed snowmelt as delayed soil-water input, which may overstate drought stress at high elevations. Transitions between Landsat sensors add uncertainty, particularly around the 2003 sensor failure. These qualifications matter when interpreting the precise mechanisms behind a pattern that the study identifies across decades.
Read the full study in Frontiers in Forests and Global Change for its methods and results.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
