In traditional copywriting, peering deep into the soul of a prospect is a standard method.
Find a strong motivator that will get a prospect to take action and play it up.
Thinner! Richer! Smarter! Sexier! Quicker! Easier! If done well, persuasive writing is the magic of turning a simple want into a must-have-it-now need.
When writing on behalf of the environment, that deep thinking must be put to use a little differently.
Whatever it is I am trying to get people to spend money on isn't going to make them thinner, richer, smarter or sexier.
It isn't going to make their lives easier or cheaper.
In fact, donating to an environmental organization arguably won't do anything to a prospect's life at all, except give them a warm feeling.
The question then becomes...
With nature what are you really selling? Let's openly admit that regardless of the higher purpose environmental organizations server, we still have to sell prospects on the idea that nature is worth their money.
How do you actually do that? Here are some of the most common ways to sell a prospect on the idea of donating to nature:

• Sell the future.
  This works for many environmental organizations whose missions line up with preservation or sustainability.
  Many environmental prospects are laser focused on the future and appealing to that urge to protect is a strong motivator, especially the young parent set.
  The key is to not make the future the only benefit your marketing highlights.
  Make sure to emphasize all you do for this generation as well.
  Even selfless parents want to reap the rewards of their donation.
  
• Tug at emotions.
  Intellectually, everyone knows we need a healthy world to support us, but pulling at a prospect's emotions will be a sure way to make them act on it.
  Why? Because no one has to donate to nature.
  Donating to an environmental cause is not something humans need for survival, regardless of what your mission statement might claim.
  So, instead of playing down theneed, play up the want.
  Pick one strong emotion, and turn the emotional pleasure of donating to an environmental cause into something that resembles an urgent need.
  
• Put the fear of the concrete jungle in them.
  This is not my particular favorite method, but worth delving into, especially if done with class and brevity.
  While I like to think that most people are already aware of what will happen if [fill in the blank with an environmental disaster here] not everyone actually thinks about it.
  And sometimes, when they do think about it, their fears are misplaced.
  Give it to them straight, with facts, about what will happen "if.
  "
• Paint a beautiful picture.
  Literally.
  While everyone with a smartphone thinks they're the next Ansel Adams, thankfully, professionals still do exist.
  And even better, they often turn their talent on nature.
  In this case, pictures work better than a well crafted description ever could and adequately pull on whatever emotion you are trying to convey.
  Why? Because your captions get read a shocking 300% more often than your body copy.
  
• Play up the science.
  If you didn't already know, people inherently believe in science and technology.
  Find those nuggets of scientific fact and deliver the message with authority.
  Actual credibility can not be understated or overvalued.
  

So...
what are you selling, specifically? It may be something different with every communication.
In fact, if you are trying to target more than one type of person, it should be a different tactic every time.
Some people are motivated by fear, and others by inspiration.
Some will be moved by facts, and others by emotions.
Using a variety of different tactics will bring in more prospects.
As I'm sure you are aware, there aren't unlimited funds waiting in the coffers for this.
The money you've earmarked is for a specific fundraising goal, and your communication methods should be working overtime to achieve it.