Forget All the Illusions
Forget all illusions and romantic stereotypes of working outside. Working outside is great and I really enjoy it, but you have to ask yourself are you the type of person who doesn't mind getting hot and sweaty in the piss pouring rain for 10 hours a day? Will you mind being knee deep in mud/animal shit or snow? Take a look at the climate you live in as you will have to be dealing with it everyday.
Scout the Job Market (First!)
Look for jobs you could get once you finish whatever course you plan to do. The trouble is that forestry is mainly carried out by the government, or at least influenced by it.
Unfortunately in times of budget cuts environmental issues are usually the first to go meaning that finding a job in the field is pretty hard here.
If you are in another country I have no idea what the job market would be like but it would definitely be some thing to look in to.
It Is A Science
Forestry is a scientific subject like any other, the question is "how can you make the most money in the quickest time".
You will see plantations where trees are grown and harvested like corn and work sites where the environment is mistreated just like the animals you mentioned. It seems like the industrial process of farming has put you off the Animal Science, but you'll often find the same sort of thing in forestry.
A plant isn't just a plant. And so there are many different paths for you to take into the forest.
For example, conservation biology. There are schools with that major, offering courses that are specifically designed with conservation in mind.
Also conservation jobs usually judge experience on the same level as education, so I would really recommend volunteering with a local organisation. Luckily these types of organisation are pretty common and only too happy to have people aboard.
You have to remember that trees take a long time to grow and therefore forestry is a very slow process.
On the Other Hand
A lot of jobs in forestry deal with the cutting down and management of forests for economic use. In fact classifying forests and soils to be cut down is where the money is.
I don't want to discourage you. We need people that are going to look at and push for better practices, but the economic driver is cutting the trees down. If you don't like how production animals are treated, you may be in for a shock to understand how we treat our forests for production. It is what it is.
A lot of jobs rely on it.
The demand for wood is huge.