GE

Then who will benefit financially?

The companies who supply genetically engineered crops, and the researchers and people they fund.

Where will the money come from?

From royalties on intellectual property in the genetically engineered crops http://www.guardian.co.uk/science/2000/nov/15/genetics.theissuesexplained

How does that work?

The farmer who grows the crops signs up to buy the seed from the supply company. The farmer is often required to use materials, such as herbicides, that also must be purchased from the supply company.

Then the farmer who doesn’t want to be involved just doesn’t sign up?

Unfortunately the genetic material belonging to the supply company is certain to eventually contaminate other cultivars on that farm through normal processes of pollination. Spread can’t be prevented anymore than the spread of possums, varroa or various weeds can be prevented. At that point the farmer is in breach of the company’s property rights and may be sued.

What is the effect of this on farmers overseas who inadvertently breach those intellectual property rights?

Some have spent hundreds of thousands of dollars to defend law suits.
http://en.wikipedia.org/wiki/Monsanto_Canada_Inc._v._Schmeiser#Judgment
http://www.dailytech.com/Monsanto+Defeats+Small+Farmers+in+Critical+Bioethics+Class+Action+Suit/article24118.htm
Some have settled and paid damages. Some have lost their farms. Some farming communities have been split as neighbours battle neighbours.
See page 17 of http://whangareileader.realviewdigital.com/#folio=16
In some countries there have been many suicides.
http://articles.mercola.com/sites/articles/archive/2012/04/03/gmo-crops-affect-farmers.aspx

How can a farmer make sure that he doesn’t inadvertently breach those property rights?

Only by not growing any cultivar of that crop species.

So if , for example, genetically engineered ryegrass were released in NZ, farmers could have no option but to grow the GE cultivar and no other, and to pay royalties to do so?

Yes

So why don’t all NZ farmers just grow the GE cultivar and forget the other varieties?

It would destroy choice. It would sacrifice a major NZ competitive advantage. There is no appetite for the products of GE in our markets. There is a large and growing market for GE free produce. Consumers in other countries are gradually learning more about the risks of GE food and the downstream effects on the environment as more studies are published.
http://earthopensource.org/index.php/news/60-why-genetically-engineered-food-is-dangerous-new-report-by-genetic-engineers
http://www.testbiotech.org/en/node/694
Growing GE crops does not make good business sense. Crops to date have been lower yielding or suffered a price penalty or both. In some cases the price penalty is 100% – there is no sale available.
http://gmwatch.eu/latest-listing/1-news-items/13882

How can these problems be prevented?

By ensuring there is no release and no field trials of genetically engineered crops in NZ.

Why then do some scientists support the release of GE crops?

Genetic engineering research and development can be profitable to the organisations they work for. Those organisations are insufficiently liable for the problems they cause for others. It also may be very exciting work (think of Jurassic Park). Further, most scientists are experts in some small aspect of their science, not in the big social, economic and environmental pictures. (See for example Bob Brockie’s column “World of Science”, Dominion Post, 15 August 2012

Other links

http://votersedge.org/california/ballot-measures/2012/november/prop-37
http://www.stuff.co.nz/dominion-post/comment/7612107/GM-free-means-good-sales-for-NZ