Plants can cause a great many problems, whether it be a bout of sickness after mistaking it for something edible or a severe rash. Some plants to avoid that are relatively common are as follows:
Pictured in center, this plant has three leaves and grows on a vine. It can creep along the ground or grow up trees. Especially old plants will even form it's own thick branches that hang out from the tree trunk. It produces a cluster of white berries and the leaves are green to a redish orange. Depending on the severity of your allergy to the plant, it can cause a irritating rash to severe swelling that requires steroids. It's relative, poison oak, also has three leaves, but they are shaped very similar to oak leaves.
This is a small shrub or tree that can get up to twenty feet tall with a thin trunk. It is considered to be far worse than poison ivy or poison oak. wiki entry
If you come into contact with these plants it is possible to avoid the rash if you wash it right away. (with in 1 hour) It is even better if you have rubbing alcohol on hand and use it to wipe the area of contact. This will destroy the oils and prevent a rash from occurring. It is the method I have used for years, while working at summer camps infested with the stuff.
There is a whole host of plants that are toxic and even deadly if eaten. Some of them even resemble edible plants. There is, however, an edibility test that you can perform. This test is mention in the military survival guide I noted in a previous article. After about eight hours with out eating take the part of a plant you want to eat and place it on the inside of your elbow and fold your arm up and hold it in there for around twenty minutes. If there is no rash, swelling or blisters, the next step is to hold it between your lips (not in your mouth) for ten minutes. If there are no issues, go one to prepare the item in the way you plan to eat it and then hold it in your mouth for around five minutes. (small quantity) If nothing happens then go ahead and swallow the small bit and wait thirty minutes. If after all of this there are no feelings of sickness, then the plant is probably safe. Start out eating small quantities. You won't starve to death in a day so it won't hurt to only eat a small bit of it that day. The next day if it is all right then you can eat more of it.
Aside from plants that are a danger there are also many animals that can harm you. The most notable would be snakes. Every one is concerned about them when they enter the forest. Did you know that the copperhead is by far more aggressive than the rattle snake? It's true, rattle snakes will give you a warning telling you to gtfo. A copper head will strike with out warning and repeatedly. They have even been known to give chase for a few feet. Their venom is not as bad as the rattler, but they're aggressive tendency makes them a bigger hazard. There are several species of snake that mimic the color patterns of venomous snakes in order to scare off potential predators. For instance the corn snake looks almost identical to the copper head.
They look a lot alike, right? Well there is a way to tell the difference. That way is by the shape of their heads. Poisonous snakes all have venom glands at the backs of their heads (except for a few exceptions) those glands give the head a very distinct shape.
One can generally tell at a quick glance if it is poisonous or not, but if in doubt get the heck out. There is no point in compounding the problems of being stuck in the woods by adding a bite on top of it. There are many other animals to worry about in the wild but they tend to be more visible and therefor a lot less scary. No one likes the idea of something jumping at them from the leaves on the ground. I recommend walking with a stick, just in case. The stick will help make traveling easier any way since it is a third point of support on the ground as you walk. And it makes a good snake bashing tool, should you come across any creepy crawlies.
Many bigger animals can be kept at bay with a few simple steps. First step is to not leave food around your camp. Bears can smell it from miles away so hang that stuff in a tree, you'll need it it to make survival easier. Fire will keep a lot of animals away. (not necessarily bears in areas actively camped) Make shift shelters do even more to keep them out. Try building one against a rock and make a barricade of timber around you.
Water is perhaps the most essential thing for life. It is also the biggest hazard in our lives. This is mostly our own fault. There are so many bacterial colonies in even the most pristine of wild waters that there is really no safe place to take a drink these days. The best way to clean it up is to boil it, but that isn't always an option and if you really have to drink then there are still a few things to make it somewhat safer.
How stuff works borrowed this from the US Army Survival Manual: FM 21-76
This is a very easy to make filtration system. The charcoal is the most important part, as just like in many store bought charcoal filters, it will neutralize a lot of stuff. How stuff works has stolen the whole article on obtaining water from the survival guide. You can find it here. (I find it amusing that they slapped a copyright symbol on pictures they took straight from the book and then just added color too)
In later articles I will go over how to build shelters and traps as well as tools and weapons.