Hi Jlim and welcome back.

Make Your Thesis Specific to the Topic

You wrote

In this essay , I will discuss the causes of this problem and find out the solutions.  

You could use this sentence in almost any essay. Don't use sentences like this! Let’s rewrite it to make it specific to the topic

In this essay , I will discuss how pollution, poaching and pressure on land are damaging the environment, and suggest some possible solutions.  

This also helps the reader to guess what is coming next.

Quotes

As old people say:''the technoloy developing faster;the level of environmental problem growing higher.''

Avoid quotes. As a famous person somewhere said, sometime, “Don’t use them.” Really. You don’t need them. If you want to use a quote, work it into the sentence as reported speech.

• My grandfather always told me to fight for what was right.
• The UAE’s Sheikh Zayed often said that a country without a history was a country without a present.
• An old proverb says that instead of giving a man a fish we should teach him how to fish.
• It’s true that a bird in the hand is worth two in the bush: sometimes we should just be happy with what we have, instead of looking for more.

Don’t use quotes about coins having two sides, swords having two edges, or time cutting you. Don’t have quotes about eating apples every day. Don’t quote your friend or “a famous psychologist.” Don’t use quotes unless you have the exact wording from a book or website in front of you, and this won’t happen in IELTS.  What am I saying? “Don’t use quotes”

Fragments

Due to the modern technology discharge a lot of sewage and gas waste to the nature.

This is not a sentence. We need to join it to the previous idea or add or delete information

Modern factories discharge toxic waste and gas into the environment.

Usage/Word Choice

1. businessmen poach the endangered species to sale ==> businessmen poach endangered species for sale OR businessmen poach the endangered species  OR endangered species are poached.
2. This will cause the endangered species extinct as fast as possible.==> This will cause endangered species to become extinct.
3. governments develop land resources to cope the surging populations. ==> Governments develop land resources to cope with surging populations. OR Governments develop land resources to cope with the surging population.
4. For example, governments can build up some organizations to advocate the important of saving the species of animals and plants like WCS （the Wildlife Conservation Society）. 
5. Organizations such as the Wildlife Conservation Society can advocate the importance of saving animals and plants. 
6. Next, governments can establish nature reserve to protect the endangered species.This action can provide animals a safely place to live and get protecting everytime. ==>
   Don’t use ‘next’ -  use ‘in addition,’ ‘also,’ ‘furthermore’.   The second sentence is not needed -  it just repeats.

 Governments can also establish nature reserves to protect endangered species.

1. People able to store or recycle waste and reduce using disposable things. ==> People can separate waste, and can reduce, reuse and recycle.
2. On the other hand, although the national budgat is very tight, governments should spend a fix money to solve the problem 
   Delete ‘on the other hand’

Although national budgets are tight, governments should allocate money to solve environmental problems

Don't worry about your level of English. You are working very hard. I wish that I could write as well as you can in another language!