The short answer is - NO, you really shouldn't. Though you may see others on the trail without even a backpack on, it does not mean that it is ok for you. Unprepared hikers pose a risk for themselves, others in their group, and anyone who may need to help them out in a rescue type situation. Some people in the wilderness, whether new or experienced, can also make the mistake of not being prepared on a simple day hike. Sometimes it is the trail that people consider easy, that might put them into a scary situation.
Most of the classic Ten Essentials lists have been updated to a system approach. Instead of just limiting you to ten items, the system makes sure to cover all necessities that can work together to keep you as secure as possible in a backwoods emergency situation. Because of this, the essentials list includes more than ten items. Since this is a list of essentials, they are in no particular order:
NUTRITION: It is important to carry enough food for a whole extra day out. So even if you are on a day hike, then you should carry two days of food. Also, be aware of those in your group whose food you are carrying. Make sure everyone has enough extra food so your personal extra supply doesn't need to support others as well.
HYDRATION: Everyone should have at least one bottle of water, but to be more safe, carry two bottles. It is also important to have the means for treating water in case you need to resupply. A water filter or a chemical treatment option. Chemical treatment, being smaller, is easy to add to a small day pack. Most water filters are lightweight and will be worth their bulkiness, depending on the type or brand.
NAVIGATION: A waterproof topographic map and compass are the most basic navigation tools to carry. Go above and beyond by bringing a GPS unit or even a description of the trail or trails you will be on. Pictures can help when trying to identify certain terrain also. If you have a smart phone then it can store some of this content, like photos and text from trail guides.
ILLUMINATION: You should always carry a flashlight or head lamp in case you happen to be on the trail past dark even if you didn't plan on it. I find that head lamps work best and some flashlights are too heavy or become awkward to carry through rough terrain. Illumination is also important for rescue if it is dark out.
INSULATION: This can vary based on climate. Extra clothing should always be packed, but you may need thicker layers if temperatures reflect that. Remember that temperatures in the mountains can be quite cooler at increased elevation. When considering your clothing in the outdoors, choose wisely by picking synthetic materials that don't hold moisture. This life saving tip includes the clothes you have on to begin the hike as well. Nylon or polyester based fabrics are used in everything from underwear to shirts.
SUN PROTECTION: The number one thing to carry for protection from the sun is sun screen. Hats and sunglasses are also recommended and nine times out of ten are already worn or packed on the trail. Umbrellas have been on the rise in popularity for hikers because of newer lightweight types that cover more area than just a hat and can be used if it rains as well. Always pack lip balm!
FIRST AID: If you choose to buy a kit that is designed for hiking needs or build your own, keep in mind the bare minimum. Blisters are very common on the trail and can become an issue if you find yourself away from the trail on an uneven terrain, so make sure to be able to treat them. Bandages of different sizes are good to have on hand because you never know what type of an injury you may obtain. It is best to have some ointment to treat abrasions and tape to help secure bandages. A lot of hikers like to pack duct tape for first aid, which can also be used for other emergency purposes. Finally, make sure you have any over the counter medications you prefer and any prescribed medication you require. You may find an anti chafe cream or ointment very helpful also.
REPAIR KIT: Knives can be one of the most handy tools for repair or emergency food preparation. Some people choose to take multi tools and others consider them heavy and unnecessary. A good alternative is to split light tools up between those in a group; pliers, scissors, knives, etc. This is a good time to bring up duct tape again as a great all around repair item for any leaks, rips, or tears. Shoelaces are a great item to pack, not only for a possible broken shoelace, but also for tying other things together. This list can get longer by adding anything extra that you are worried might break on your pack or tent; like ties or buckles.
SHELTER: If you are backpacking then you most likely have a shelter, but if you are out on a day hike, then consider these options. A bivy sack is all inclusive keeps you warm and is advertised as waterproof. A lightweight tarp is great, but should be accompanied with an emergency blanket or even a garbage bag. Some hikers also use garbage bags to line their packs and keep everything dry inside.
FIRE BUILDING: Waterproof matches are a staple item because they will light in most situations. Carry a small lighter and try that first, for if it fires up, then you save your last resort and get instant flame. Some people pack a flint of some sort or even bring tinder from home. Dryer lint is a great fire starter! It is best to keep these items as dry as possible. It is very important to know how to start a fire in the woods without the amenities of your house. You will most likely be dealing with wet wood and tinder. Note: Only extreme emergencies allow for fires in non designated areas. Make sure you know the rules of the land you will be hiking on!
Above and beyond this essentials system you might want a protection from insects! Biting flies, ticks and of course mosquitoes can ruin a trip and make an emergency situation worse. There are sprays and even a handy head net that can save you from complete loss of mind. Another item, that is sometimes accompanied with something else already in your pack, is a reflector. Compasses or multi tools might have a reflector that can help if you need to be located. A personal locator beacon is a costly item that will ensure rescue if used properly. Some packs have a built in whistle which can also help for location purposes. If not, then consider adding one to your essentials list. I think a smart phone is a great resource as stated above for holding information. There are some apps that work in airplane mode that help with navigation by using satellites. Also, email yourself all of the trail information and backup maps to have references if needed.
REI actually has a great list: http://www.rei.com/learn/expert-advice/day-hiking-checklist.html
By Rudy Giecek