Seminar 5 2011 Question Page

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Harnessing Biodiversity 2011 - Questions Page

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Biodiversity Loss

Catherine T, Aorere College

What is the main cause of the biodiversity loss worldwide?

Alexander H, Horowhenua College
Can there be such a thing as too much diversity in nature? Will exploiting every ecological niche have an adverse effect on the ecological environment? And can increased diversity have an adverse effect of ecology?


Fardowsa M, Massey High School
What is the negative effect of reduced biodiversity associated with monoculture on people? Why is monoculture considered better than the alternative for food production today? A why have we resorted to monoculture if it is detrimental to our world's biodiversity?

 Steve Wratten, Bio-Protection Research Centre, Lincoln University Live seminar response June 23, 2011

This is a very interesting question. If we do not have biodiversity in farming we have to practise substitution agriculture; we use fertilisers instead of natural nitrogen; we use insecticides instead of natural management of pests. This means that our food is in danger of having been grown as a monoculture which has a high input of toxins and probably high levels of fertilisers. High levels of fertiliser usage gives rise to three problems. Firstly, it is made from oil, which is running out; secondly the run-off pollutes rivers; thirdly it is getting more expensive as oil prices go up. Every year people around the world are killed by pesticides. Traces can be found in our food, tiny amounts can be unhealthy and people and markets don’t want the pesticides in food. This use of pesticides reduces biodiversity and is referred to the pesticide treadmill – once you are on it you cannot get off.

Monoculture is considered better than alternative food production because the yields are high. This needed if we are to ever feed the world’s population. Does a better biodiversity mean we can’t have higher yields? Not necessarily but it does mean we can lower costs.

The term biodiversity has been around since Edmund Wilson invented the word in the United States the 1970’s. We now recognise that we can improve biodiversity on farmland easily and cheaply and this is a new science.

David B, Sacred Heart College
Doesn't using other species reduce the amount of crop you get per square km even if the cost of chemicals and such is reduced? Because isn’t the most important thing to produce lots of food if we are aiming to feed the world?

Georgina B, Lincoln
Would optimal biodiversity be obtained by backing off and letting nature take its course?

Bees and other species

Georgina B, Lincoln High School
But if bees are lost, won’t a superior organism eventually fill their niche?

Jaedan P, Onehunga High School
How can you tell (in advance) whether or not a new introduced predator will attack the pests or your natives that aren’t pests?
Steve Wratten, Bio-Protection Research Centre, Lincoln University Live seminar response June 23, 2011

The cabbage white butterfly that is now all over New Zealand, came into New Zealand on the sailing ships in the 1860’s. In England, in the 1930’s, they found a parasitic wasp that kills the white butterfly by laying eggs in the larvae. So the wasp was introduced into New Zealand. The wasp did lay eggs in the white butterfly caterpillar but it much preferred laying its eggs in the larvae of the endemic red admiral butterfly.

To ensure that this type of mistake does not occur again screening is done in labs, for up to two years. The wasp is tested against a wide range of species e.g. green fly, grass grub, native butterfly. Only when it is certain that the wasp will kill only the target species will it be released. When biocontrol is good it is very good, but when it is bad it is unbelievably bad. New Zealand scientists, with government regulation, are being very careful that the mistakes made in the past do not happen again.

Sue U, Lincoln University
What can you tell us about the proposed introduction of dung beetles in NZ? What sort of impact on the ecosystem and other species can we expect?
Steve Wratten, Bio-Protection Research Centre, Lincoln University Live seminar response June 23, 2011

I wonder how effective they will be. Firstly, you do not often see dung pats on dairy farms as the cows seem to produce “liquid” faeces. The introduced dung beetles lay eggs in dung pats, rolling them into a ball and bury the ball in the ground. The beetles come from countries such as Australia where they roll the dung of kangaroos and wallabies; in Africa there are antelope, elephant and giraffe, all producing large quantities of dung. My concern would be how effective these beetles would be in a paddock in New Zealand. Secondly, nearly all the biodiversity in our farmland is introduced e.g. earthworms introduced from Europe. Do we need more insects from outside New Zealand on our farmland? They may not behave like the stoat, but I am naturally nervous about these things.

Land use

Alexander H, Horowhenua College
Have you got any suggestions for practical solutions for the agricultural negative impact on biodiversity? What do you think is the biggest limitation to effecting a positive change in our impact? Steve Wratten, Bio-Protection Research Centre, Lincoln University Live seminar response June 23, 2011

Another very good question and the students are to be congratulated on the quality of these. The solution is sometimes called ecological engineering, where the landscape is planted in an almost surgical way. For example, do we need borage around the potato? What the best plant for vineyards? Buckwheat. What about grass grub in pasture? With enough research we can precisely analyse the different ecosystems we have and work out what to do. But not every vineyard is white from the buckwheat, crops of sweet corn are not surrounded by strips of blue. The biggest limitation is that the science is new but farmers, worldwide, are conservative and slow to change their practise. If scientists are not communicating their science to people outside their work then they are at fault. If they have data then they need to communicate it to the right people, share it with farmers, show them what it looks like in the field and give them a dollar value.

Alexander H, Horowhenua College
How does crop rotation affect the monoculture issue? Does this old system go some way to fixing the problem?

Pests and weeds

Fardowsa M, Massey High School
Is there controversy in the definition of what is a weed – or a pest?

Kate H, Havelock North High School
What is your opinion on the use of 1080 for possum control?