The Forest Landscape Integrity Index (FLII) is a global, map-based indicator of forest condition that estimates the degree of anthropogenic modification of forest ecosystems. Developed by an international research team led by the Wildlife Conservation Society, the index integrates spatial data on observed and inferred human pressures and loss of forest connectivity to produce a continuous score from 0 (most modified) to 10 (least modified) for each ~300 m forest pixel.

In the study's global map for early 2019, 40.5% of forest area (about 17.4 million km2) was classified as high integrity (FLII ≥ 9.6), 33.9% (14.6 million km2) as medium integrity and 25.6% (11 million km2) as low integrity (FLII ≤ 6.0). High-integrity forests were concentrated in boreal regions of Russia and Canada and in large tropical forest blocks such as the Amazon, Central Africa and New Guinea.

FLII has been used in forest-condition monitoring and referenced in policy and research contexts, including discussions of ecosystem integrity indicators under the Kunming-Montreal Global Biodiversity Framework.

Forest integrity In ecology, ecological integrity (sometimes ecosystem integrity) refers to the extent to which an ecosystem's structure, species composition and ecological processes fall within their natural range of variation. In forests, integrity is often discussed alongside, but distinct from, deforestation (area loss) and forest degradation (declines in condition or function without complete land-cover conversion).

The FLII operationalizes forest integrity as the inverse of cumulative human modification at the landscape scale, combining mapped pressures, modeled indirect effects and changes in connectivity to generate a globally consistent, continuous integrity score.

Methodology Grantham et al. calculated FLII by integrating four main spatial inputs—forest extent, observed pressures, inferred pressures and loss of forest connectivity—with processing carried out in Google Earth Engine.

Forest extent and temporal baseline The forest extent layer was designed to represent forest at the start of 2019. Forest was defined as woody vegetation taller than 5 m with at least 20% canopy cover. To map extent, the authors used global tree-cover estimates for 2000 and subtracted mapped tree-cover loss from 2001–2018 (excluding temporary canopy loss).

Observed and inferred pressures Observed pressures represent human activities that can be mapped directly at global scale (e.g. built infrastructure, agriculture and recent deforestation). Inferred pressures represent additional impacts that tend to occur around observed pressures but are harder to map directly (e.g. access-related extraction such as selective logging, fuelwood collection and hunting), modeled as a decay function of proximity to observed pressure sources and access networks.

Connectivity loss The connectivity component estimates reductions in forest connectivity caused by forest loss and fragmentation, capturing the influence of surrounding forest cover on a given pixel's integrity.

Scores and classes The continuous FLII ranges from 0 to 10. For communication and reporting, the authors also provided an illustrative three-class map: low (≤6.0), medium (>6.0 and <9.6) and high (≥9.6), with thresholds benchmarked against reference locations of known ecological integrity. The study noted the approach could be updated as new global datasets become available, including potentially on an annual basis.

Global results In the 2019 map, the authors estimated that 91.2% of the world's remaining forests were affected by some degree of human pressure, and 31.2% experienced observed pressures. They reported a global mean FLII score of 7.76; 18 countries had mean scores greater than 9, and no biome or biogeographic realm contained more than half of its forest area in the high-integrity class.

High-integrity forests were disproportionately concentrated in a small number of countries (with Russia and Canada together containing about half of the global high-integrity forest area). Only about 27% of high-integrity forest area fell within nationally designated protected areas, while 56% of forests within protected areas were classed as high integrity.

Country rankings 172 countries have been ranked: +Forest Landscape Integrity 2019 Country Mean FLII Low integrity (km2) Medium integrity (km2) High integrity (km2) Total forest area (km2) Map 10 0 0 68 68 9.8 1 72 495 569 9.58 4,162 40,817 147,413 192,391 9.45 5,083 59,389 146,218 210,691 9.39 6,796 25,031 107,954 139,781 9.36 520 11,915 27,407 39,841 9.28 30,161 139,350 379,097 548,608 9.13 13 187 372 572 9.07 11,780 118,348 120,852 250,979 9.02 739,484 2,245,281 5,137,079 8,121,843 8.99 480,206 1,027,386 2,968,268 4,475,860 8.89 24,512 124,215 158,184 306,911 8.86 329 2,819 2,761 5,909 8.86 85,793 190,547 509,720 786,061 8.85 90 1,475 977 2,542 8.85 1,620 16,769 10,140 28,529 8.84 37,294 183,415 216,355 437,064 8.82 734 5,322 4,448 10,504 8.78 64,650 170,792 351,112 586,554 8.65 34 137 130 301 8.47 78,745 280,532 272,007 631,284 8.43 5 13 17 36 8.35 105,487 284,054 315,895 705,436 8.35 1,753 10,802 3,594 16,148 8.26 150,737 272,442 428,320 851,499 8.23 6,068 18,926 15,294 40,288 8.09 45 333 9 387 8.02 8,374 40,156 8,410 56,939 8 66,191 181,336 119,263 366,789 7.99 3,982 17,595 5,007 26,585 7.79 6,982 17,803 9,784 34,570 7.71 1,102 2,842 1,498 5,442 7.69 284 1,149 82 1,515 7.67 3,361 12,930 2,162 18,453 7.66 48,822 77,585 73,492 199,900 7.56 533,118 935,508 727,983 2,196,608 7.55 8 35 0 43 7.52 1,374,902 1,354,961 2,338,101 5,067,963 7.5 96,969 164,376 110,822 372,167 7.42 2,034 7,090 459 9,583 7.42 2,090 7,859 1,139 11,088 7.4 1 4 0 5 7.37 56,849 41,971 93,537 192,357 7.35 741 1,935 399 3,075 7.23 13,785 41,992 3,760 59,538 7.22 117,672 239,624 103,852 461,148 7.21 98,249 189,966 72,557 360,772 7.19 6,871 15,310 3,149 25,329 7.18 129,745 220,188 96,924 446,857 7.16 52,652 84,430 44,397 181,479 7.16 451 996 140 1,586 7.16 347 1,384 46 1,777 7.14 533,800 974,431 301,051 1,809,282 7.13 123,997 159,712 122,812 406,521 7.12 34,503 44,155 35,334 113,992 7.11 847 2,456 162 3,465 7.11 1,783 7,008 47 8,838 7.09 117,992 254,792 54,428 427,211 7.06 388 1,026 18 1,432 6.98 39,343 67,383 16,627 123,352 6.95 91 221 0 312 6.93 150,665 189,362 115,379 455,406 6.82 193,908 280,445 121,842 596,195 6.77 2,426 5,256 122 7,805 6.77 214 227 199 640 6.74 2,260 4,076 451 6,787 6.65 1,328,079 1,144,693 658,645 3,131,417 6.64 31 140 0 171 6.62 1,478 2,176 418 4,072 6.6 14,548 27,833 1,078 43,459 6.6 535,370 509,018 431,973 1,476,361 6.55 4,820 7,189 1,534 13,543 6.41 2,949 4,778 82 7,809 6.39 78,538 102,626 29,877 211,041 6.39 43,043 68,243 3,516 114,801 6.38 8,786 14,547 1,453 24,786 6.37 27 38 0 65 6.37 25,420 21,310 14,605 61,336 6.31 30,143 31,939 16,349 78,431 6.31 5 33 0 37 6.31 9,450 14,417 1,644 25,511 6.2 64,621 65,355 24,307 154,283 6.18 5,261 6,016 1,910 13,187 6.17 235 316 0 551 6.15 7,004 7,957 2,744 17,705 6.09 18,884 26,325 847 46,057 6.02 25,060 32,009 888 57,956 6 86,276 89,326 33,612 209,214 5.99 13,387 17,031 574 30,993 5.95 38,395 48,394 607 87,395 5.91 91,820 100,831 8,393 201,044 5.88 5,064 4,522 1,076 10,662 5.86 4,724 3,698 1,769 10,191 5.83 20,541 22,390 1,613 44,544 5.8 135,783 133,480 16,005 285,268 5.74 12,514 12,167 2,396 27,078 5.7 9,274 8,702 855 18,831 5.59 92,986 80,564 19,252 192,801 5.46 1,894 1,681 3 3,577 5.46 567 478 0 1,045 5.45 10,013 7,251 1,947 19,211 5.4 22,605 18,460 1,632 42,697 5.35 174,415 109,779 23,494 307,687 5.35 82,551 75,353 9,588 167,492 5.29 17,513 14,112 516 32,141 5.22 7,418 6,044 81 13,543 5.19 2,628 1,775 47 4,450 5.14 1,354 987 0 2,340 5.08 144,310 83,572 9,294 237,176 5.01 5,362 3,249 158 8,770 5.01 130,825 91,957 21,499 244,281 4.94 45,489 34,968 3,196 83,653 4.92 15,732 10,522 379 26,633 4.9 81,702 54,877 2,895 139,475 4.85 15 2 0 17 4.79 51,975 31,162 11,025 94,163 4.72 114 92 0 206 4.65 27,164 12,838 4,164 44,167 4.63 120,340 66,584 11,922 198,846 4.56 181 85 0 266 4.55 95 50 0 145 4.53 57,519 28,901 2,160 88,580 4.52 161,987 49,496 74,121 285,604 4.5 6,882 3,841 46 10,769 4.5 59 42 0 101 4.48 57,899 23,802 3,692 85,392 4.45 170 49 0 219 4.36 77,303 36,381 7,507 121,190 4.34 17,615 8,165 0 25,781 4.23 82,770 46,013 133 128,916 4.22 221 86 0 308 4.21 5,054 2,501 14 7,569 4.2 28,427 13,558 4,702 46,686 4.19 19,890 9,364 518 29,772 4.14 170 85 0 255 4.05 8,837 2,947 0 11,784 4.01 7,116 2,831 12 9,959 3.85 58,572 18,764 5,592 82,928 3.85 5,665 2,170 619 8,454 3.78 11,065 3,791 0 14,856 3.76 541 115 0 656 3.65 79,403 26,858 25 106,286 3.64 158,010 41,005 7,288 206,303 3.64 841 282 0 1,123 3.63 77,870 20,847 91 98,808 3.63 65,356 17,646 4,858 87,860 3.61 11,793 3,998 0 15,791 3.59 104 9 0 113 3.55 36,666 12,422 21 49,109 3.53 13,636 4,412 10 18,058 3.3 89,540 20,183 176 109,900 3.05 24,473 4,832 52 29,358 2.79 12 0 0 12 2.76 52,512 11,858 640 65,010 2.28 122,168 11,307 0 133,475 2.25 18,729 2,047 0 20,776 2.24 101,886 7,103 0 108,989 2.2 3,113 202 0 3,315 2.09 38,164 2,137 0 40,301 1.71 32,161 1,611 0 33,772 1.65 29,149 2,917 35 32,101 1.62 24,554 930 0 25,484 1.36 8,803 297 0 9,099 1.12 1,170 0 0 1,170 1.11 170 2 0 172 1.06 531 2 0 533 0.92 5,283 96 0 5,378 0.82 25,966 553 0 26,519 0.6 5,250 72 0 5,322 0.56 4,772 218 69 5,059 0.5 5,756 31 0 5,787 0.01 7 0 0 7

Use and applications Policy and reporting FLII has been referenced as a complementary indicator for monitoring ecological integrity, connectivity and ecosystem restoration under Target 2 of the Kunming-Montreal Global Biodiversity Framework. The World Resources Institute's Global Forest Review uses FLII as a measure of forest degradation in its synthesis of global forest change and condition.

The 2023 Forest Declaration Assessment includes "FLII units lost per year" as an indicator of forest degradation for tracking progress toward international forest goals.

The European Commission's Joint Research Centre has incorporated a Forest Landscape Integrity layer in its Global Forest Types 2020 map product and related "primary forest" outputs.

Research Researchers have used FLII to compare forest condition across governance and conservation regimes. For example, Sze et al. (2022) used FLII in a pan-tropical analysis of forest integrity across overlaps of protected areas and Indigenous peoples' lands.

Crowe et al. (2023) applied FLII to assess forest integrity within thousands of Key Biodiversity Areas (KBAs), highlighting its potential role in monitoring the condition of biodiversity-important sites. BirdLife International has used FLII-based analyses to communicate trends in forest integrity within KBAs identified for forest species.

FLII has also been used as an input or comparison layer in composite integrity metrics and validation studies, including an ecosystem integrity index integrating multiple global datasets and field-based evaluation of how FLII corresponds to ecological indicators in boreal forests.

Standards and finance The High Integrity Forest (HIFOR) methodology incorporates FLII thresholds in eligibility criteria for "high integrity" forest areas in its monitoring framework.

Limitations The original study described FLII as a conservative estimate and noted several limitations. Some pressures are difficult to map consistently at global scale (e.g. finer-scale infrastructure or small-scale extraction), and forest modification prior to 2000 may not be reflected in the underlying global datasets. The authors also noted that the index does not explicitly account for all drivers of integrity loss (such as climate change and invasive species), and that the forest extent definition can include tree crops and plantations, which typically score as low integrity under the model.

Data and availability An interactive map and downloadable data products (including continuous and classified layers) are provided via the project website.

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