The Wallace Line is an invisible biogeographical boundary running through the Indonesian archipelago. It marks a sharp average change between Asian-associated animals on the Sunda Shelf and Australian-affiliated animals linked to the Sahul Shelf.
It is not a wall, and species do cross it. Its power comes from deep ocean gaps that remained underwater even when ice-age sea levels exposed the shallower shelves on either side. That geography restricted many land-animal dispersals for millions of years, producing one of biology’s clearest regional transitions.
What the Wallace Line is
The Wallace Line is a scientific model for a major change in animal communities, not a visible feature on a map. Alfred Russel Wallace recognized that neighboring islands could have strikingly different mammals, birds and other terrestrial animals. The line broadly separates fauna with Asian evolutionary histories from fauna associated with Australia and New Guinea.
“Later known as Wallace’s Line, this marked the boundary between the animal life of the Australian region and that of Asia.” — Natural History Museum, institutional explainer, accessed 2026.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Special offer. See more information about Outbyte and uninstall instructions. Please review EULA and Privacy policy.#1 Best Overall
Swiftmaps World Premier Wall Map Poster Mural 24h x 36w Paper Folded
- FOLDED EDITION - portable 8x10 inch folded size
- WORLD MAP is printed on 24lb paper
- 3D SHADED RELIEF: 3D shaded visual terrain relief for land and oceans
- PERFECT world map for business, home or educational use
- UP-TO-DATE: completely current world wall map poster
Modern biogeographers usually describe the line as the western edge of Wallacea, the island region between the Sunda and Sahul continental shelves. Wallacea covers about 347,000 km² of land, according to the Research Centre for Geotechnology of the Indonesian Institute of Sciences (page accessed 2026).
Where it runs through Indonesia
NOAA traces the boundary from the Celebes Sea through the Makassar Strait between Borneo and Sulawesi, then through the strait between Bali and Lombok. The exact placement is a convention describing a broad transition rather than a surveyed fence with one universally agreed coordinate. Its historical interpretation, especially around Sulawesi, has changed as more groups and deeper evolutionary lineages have been studied.
Why deep water creates such a strong divide
The physical explanation is the arrangement of continental shelves and ocean basins.
Rank #2
- Updated
- Each Poster 18" tall x 29" wide
- High-quality 3 MIL lamination for added durability
- Tear Resistant
| Geographic element | Role in the pattern |
|---|---|
| Sunda Shelf | A relatively shallow shelf connecting mainland Southeast Asia with Sumatra, Java, Borneo and Bali. During glacial low sea levels, large parts could become continuous land. |
| Wallacean gaps | Deep-water straits and basins separating the islands between the shelves. The deepest passages remained marine even during ice-age lowstands. |
| Sahul Shelf | A shallow shelf linking Australia and New Guinea. Lower sea levels could also expose parts of this shelf and join its land areas. |
This means an animal that could walk across an exposed Sunda or Sahul landscape still faced a marine barrier before reaching the other shelf. Water-depth contrasts and repeated sea-level changes therefore amplified separation between populations. A study in the Zoological Journal of the Linnean Society identifies these deep-water gaps, together with glacial sea-level change, as major limits on dispersal.
Geology adds a longer timescale. A 2026 review from the Indonesian Institute of Sciences links the present arrangement to deep-water barriers inherited from complex Cenozoic tectonics, later altered by Neogene plate convergence and Quaternary changes in climate and sea level. The modern pattern reflects plate motion, island-arc formation, persistent ocean gaps and repeated shoreline shifts—not climate alone.
How Wallace recognized the pattern
Wallace spent eight years collecting in the Malay Archipelago, from 1854 to 1862. The Natural History Museum records 125,660 specimens, including more than 5,000 species new to Western science (page accessed 2026); National Geographic likewise describes more than 125,000 specimens gathered during the expedition.
Rank #3
- UPDATED WORLD MAP: This map series is completely up-to-date with all current country boundaries.
- LARGE WORLD MAP: Large 32" (high) x 50" (wide) size world map is perfect for almost any wall size.
- LAMINATED WORLD MAP: Each world map is laminated on both sides with a durable 3mil lamination. Perfect for dry erase use if needed.
- WORLD MAP POSTER: Great world map poster for many uses. Home/Office decor, home schooling or even classroom use.
- SWIFTMAPS WORLD MAP: Production and Cartography by Swiftmaps - One of the leading wall map manufacturers in the United States!
By comparing distributions from island to island, Wallace saw that the change in animal life could be abrupt even where islands were geographically close. He proposed an imaginary dividing line to represent that transition. His travel book, The Malay Archipelago, remains the most direct primary-source account of his journeys, observations and collecting.
Can animals cross the Wallace Line?
Yes. “Barrier” is shorthand for a strong statistical filter, not an uncrossable border. Storms, rafting, flight, swimming, human transport and other forms of dispersal can move organisms across the gaps. Whether a newcomer establishes a population depends on the distance, its biology and the ecological conditions it encounters.
Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchPC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Dispersal ability changes the result
Flying animals and organisms capable of surviving accidental ocean crossings are more likely to appear on both sides than strictly terrestrial, poor-dispersing animals. The line therefore predicts community differences most reliably when the organisms being compared have similar movement limits.
Rank #4
- Extra large wall map is the largest world map available as a single printed sheet: this giant map of the world measures an enormous 46 x 80 inches, with a 1:20m scale, making it an eye catching addition to any room. Perfect map for your back to school supplies.
- Updated in 2026: high level detail political map of the world features colored countries, clear towns and cities, and the world map is finished with hill and sea shading.
- Write-on world map: heat sealed between two sheets of industrial quality film, this map is laminated and perfect as a classroom world map as it can be written on with whiteboard pen and wiped clean.
- Crease-less delivery: your huge world map poster is rolled in a tube for delivery, so it arrives ready to display.
- Maps international: our philosophy of ‘cartographic excellence’ combines detail, design and high quality finishes in a range of stunning wall maps.
Arrival does not guarantee persistence
Colonists must also survive competition and predation from established island species. A species can cross yet remain rare, fail to reproduce or disappear, leaving little lasting signature in the regional fauna.
Evolutionary depth changes the map
A peer-reviewed synthesis finds biotic mixing across the line and shows that results vary with taxonomic depth. Sulawesi can appear on the western side of the divide for birds when deeper lineages are compared, while mammal patterns can look admixed. These findings do not erase the transition; they show why it should be treated as a flexible biogeographical boundary.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why plants do not fit a simple two-sided model
Plants provide an important limit to the classic formulation. An analysis of 7,340 species, published in the Biological Journal of the Linnean Society in 2011, found stronger support for a three-region division of Malesia than for a simple two-region Wallace Line model.
Best Value
- Classic Edition Decor That's Also a Real Reference: A 50" x 32" decorative-yet-functional world wall map with antique-style accents that give it an upscale, library-shelf feel while keeping the up-to-date political boundaries and place names of a current Rand McNally reference map
- Color-Matched Topographical Relief: Mountain ranges, plateaus and elevation changes shown in a coordinated color palette for at-a-glance identification of major physical features around the world
- Africa-Centered Projection: A less-common projection that allows viewers to see every continent and country complete and intact — without the splits and edge-distortions of standard Pacific- or Atlantic-centered maps
- Laminated for Durability, Rolled for Shipping: Laminated to resist scuffs and fingerprints in classrooms, offices and homes; ships rolled in a white cardboard tube with cap to arrive crease-free and ready to hang
- Trusted Since 1856 — Made in the USA: Rand McNally has been the most trusted source for maps, directions and travel content for 170 years; designed and printed in the United States
That result does not make the line useless. It shows that its explanatory strength depends on the taxon, the traits being measured and the evolutionary level of comparison. A boundary that works well for many land animals cannot automatically be applied to every plant, insect or microbial lineage.
Wallace’s Line, Wallacea and Lydekker’s Line are different terms
- Wallace’s Line: The western biogeographical boundary describing the main Asian-to-Australian faunal transition.
- Wallacea: The island region between the Sunda and Sahul shelves, where the deep-water barriers and mixed evolutionary histories occur.
- Lydekker’s Line: A separate boundary used on Wallacea’s eastern side. It is not another name for Wallace’s Line.
Using the terms interchangeably can make a map or species claim seem more absolute than the evidence supports.
Why the boundary matters to biology
The Wallace Line helped establish biogeography: the study of where organisms live and how isolation, geological history, dispersal and evolution produce those distributions. Wallacea is especially valuable because its islands combine exceptional endemism with a complicated geological history.
The region also demonstrates why present biodiversity cannot be explained by today’s climate alone. Ancient shelf connections, ocean depth, plate movements, repeated sea-level changes and ecological interactions all leave detectable marks on which animals occur together. The line is therefore both a practical guide for interpreting species maps and a case study in how Earth history shapes living communities.
The Tool Desk
Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Quick Recap
How to read claims about the Wallace Line
- Expect a sharp change in average community composition, not an empty zone.
- Check whether the claim concerns mammals, birds, plants or another group; boundaries differ among taxa.
- Ask whether the comparison uses present-day species or deeper evolutionary lineages.
- Separate natural dispersal from movements caused by people.
- Treat the mapped position as a biogeographical convention that may be refined around Sulawesi and other complex islands.
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.
