Flora: In general, the endemic and island-adapted flora of Maui are very benign. Things like poison ivy are rare if nonexistent. Kiawe Trees have really nasty thorns that can penetrate hard rubber soles. Don’t underestimate them, especially when they are buried in the sand.

Fauna: The biggest wild animal you will encounter are the feral pigs that roam the more natural parts of the island. Ruinous to the endemic rainforest, you can tell you’re in a pig area by the obvious damage done to the tree ferns. Encounters with humans are rare and a feral pig will probably run away from you, but they can be quite large (up to 200 pounds) and deserve your respect. There are a few species of scary-looking spiders like the cane spider, but none are poisonous (although a few are venomous and can leave a painful bite). There are no snakes (or shouldn’t be). The worst thing you can encounter is the notorious Hawaiian centipede. They can be black, bluish, or red, and can grow to six or so inches long. The bite is said to be intensely painful (but not life threatening). There is no antidote, and a local legend says to just stay drunk for a few days. Centipedes thrive in wet, warm places. Mosquitoes congregate in certain locations on the island, and their possible presence is noted on several hikes on this site.

Hypothermia: While hypothermia is likely less of a concern along the coasts, it is an ever-present concern in the higher areas of Maui. Hypothermia results when your body’s internal temperature drops to a point (about 95 degrees) where your brain reacts by beginning to shut down non-essential systems. Common symptoms of mild hypothermia are confusion and severe shivering due to chills. Serious hypothermia can result in organ failure and death. The key to avoiding hypothermia is proper clothing and gear. Always carry raingear in the rainy, cool parts of Maui. Cotton clothing exacerbates heat loss. Polyesters and wool, on the other hand, retain warmth when wet.

Heat Injuries: While hypothermia occurs when body temperature drops, hyperthermia occurs when the opposite occurs. Heat injuries are a big concern when hiking in any coastal region. Mild symptoms can include reddish skin, confusion, vomiting, diarrhea, nausea, and clammy skin. Heat injuries typically occur as a result of overexertion in the outdoor hiking context. Avoiding heat injuries is fairly simple: hike at a moderate pace; take scheduled breaks in the shade; drink and carry plenty of water; consider covering bare skin with light-colored long pants and shirts made of polyester; wear a hat that shades the sun; wear sunscreen; and above all know your limits.

Dehydration: The tropical sun in Hawai’i is unrelenting. Despite the humidity in the air, you’ll need to drink and carry water as if you were in a desert. Dehydration can occur faster than you think, so drink water before you’re thirsty. If you’re partying at night, note that alcohol can exacerbate dehydration.

Acute Mountain Sickness (AMS): This only applies if you are going to visit Haleakalā National Park. This serious medical condition is a result of a lack of oxygen in the atmosphere at higher altitude, so if you don’t intend to visit Haleakalā National Park, don’t worry about this. If so, read this extended discussion of Acute Mountain Sickness. 

Water (freshwater rivers and streams): Water crossings of any kind should be carefully evaluated on Maui. This is constantly-changing land. Swift rivers and streams kill people every year in Hawai’i. Always consider flash flood danger and understand that it doesn't matter if it's raining where you are -- it only matters if it's raining upstream. There are a few hikes on this site that require you to cross flowing freshwater. When in doubt, use a rope -- or turn around and come back another day. 

Water (drinking): Treat all sources of freshwater on Maui before drinking. There are no known freshwater sources that are safe. Giardia and Cryptosporidium are common, as well as some other less common parasites. Beyond parasites that you ingest via drinking water, Leptospirosis spirochetes can enter the body via soft tissue, such as open cuts or sores, the nose, ears, and mouth. Avoid swimming in freshwater if you have open cuts or sores, and consider keeping your head above water in areas known to contain Leptospirosis. This disease usually doesn't show symptoms until two weeks after expsoure and can be fatal. If you feel sick with flu-like symptoms a few weeks after hiking or swimming in freshwater sources, seek medical attention immediately and inform your healthcare provider that you might have been exposed to Maui freshwater parasites. 

Water (ocean): If the rivers and streams weren’t dangerous enough, the ocean around Hawai’i  is extremely dangerous and claims many lives every year. None of the hikes on this site require you to swim in the ocean, but several lead you to beautiful beaches. This beauty usually comes along with strong rip currents and submerged, dangerous lava. Never turn your back to the ocean. If you get caught in a rip current, calm down, let it drag you out, and then swim parallel to the beach to escape its grasp. Don’t assume that it’s possible to swim at every beach, no matter what you’ve heard or read. Carefully research and evaluate the options. Talk to locals. A few hours can drastically change beach conditions. Sharks, as usual, are an overblown but present threat in the waters. Avoid them by staying out of murky water, especially at dawn and dusk. Sea urchins are present in many offshore areas, and you really don’t want to step on one. Water shoes help a lot to avoid them, and the sharp lava too. A more pressing concern in the ocean is Portuguese man-of-war jellyfish that probably won’t kill you but will certainly ruin your day. If you get stung, first remove any remaining tentacles from your skin with a stick or gloved hand with freshwater or seawater to rinse. Don’t put anything else on the wound. None of the absurd old wives' tales work – not vinegar, not urine(!), nor any of the things they sell in stores. These methods are either scientifically inconclusive or can even make it worse (especially urine – please don’t piss on your hiking partner, literally or figuratively). Apply hot or cold depending on which feels better to the victim. Contact emergency medical services if cardiac issues or severe confusion develops in the victim.

Tsunami: It’s not a major concern, but is worth mentioning. When you’re in any coastal region of Maui, you’re in the tsunami danger zone. Almost every state and county road contains a sign at about the 500’ level indicating safety from these killer waves. If you hear sirens, head quickly for land above these signs.

Theft at Trailheads: This isn’t a major problem, but does occur at some popular trailheads. Locals, mostly teens, sometimes case popular parking lots at trailheads to engage in petty theft. Rental cars are obvious, as are tourists. It’s a crime of opportunity: wait for tourists to load up a backpack and head off down the trail, and then break into their car once they are gone. The best way to avoid theft is to leave nothing of value in your car and leave the doors unlocked. Don’t put anything in the trunk.