I strongly agree with Artur. Biodiversity is never negative. I believe that an ecocentric vision, with man taking part of ecosystems would be recommendable. Then, top predator fishes accumulate mercury because this element is somehow in the water, not because of high biodiversity.

Now we are facing a modern "biodiversity crisis", right? A large part of this crisis is due to human activities. I am afraid that an anthropocentric view of nature conservation would justify those who don't care of conservation at all. So, I believe that the best approach to conservation is the ecocentric approach, with man and its sustainable activities as key element of ecosystems, but NOT at the center of nature. Anthropocentrism is a dangerous approach, because it can be strumentalised.

I haven't intended to start a discussion about anthropocentrism here, but I invite you to read a text I wrote on this topic on my blog: http://zielonygrzyb.wordpress.com/2014/07/19/in-defence-of-anthropocentrism/ Critical comments are welcome.

Drogi Panie Arturze (let me start this way to show good intentions),

I cannot recollect suggesting anyone to be dumb. If you mean the sentence "And anthropocentrism is not as dumb", all I meant was that anthropocentrism needn't be as simple and myopic as you seem to view it. Yes, it is based on a human-centric perspective, but this does not mean that it must be dangerous to nature. See the link above.

"axiology based on "our" good is not really fruitful when it comes to biodiversity." As you might have noticed, I disagree. But this is not really the point here.

My focus (the question I asked has to do with the research I am doing within my PhD thesis) is not on "biodiversity" as a synonym of "nature", but on the diversity aspect. This means that I am not interested in individual species, but in their multiplicity. I know that my question was formulated rather vaguely, but I didn't want to write a huge text just to explain what I mean by "biodiversity" - I also hoped that the examples will suffice.

Dear Bartosz, it seems to me that you are "walking around the central problem". Your intention is not to start a discussion on anthropocentrism, ok. However, your approach is anthropocentric, isn't it? It assumes anthropocentrism, doesn't it? If so, I believe that negative criticism on anthropocentrism is not out of place.

Dear Ferruccio,

it depends on the perceived aim of my question. For me, it is just a way to fill one little gap in my PhD thesis. I have no problem with discussing anthropocentrism, but I also hope to get an answer to my original question. Therefore I would prefer to move the anthropocentrism discussion elsewhere. As my blog is accessible to anyone and I happen to have written on that topic already, it seems to me that this is a more proper place to discuss this than under my more specific and "prosaic" ResearchGate question.

Ok, your question is "Biodiversity/species diversity can have negative effects on human well-being"? My answer is: "no it cannot, never".

I tend to agree with the above answers. Biodiversity drives ecosystem services, all which have a value for human settlements. In addition your statement above about increase in biodiversity increasing pathogens and pests is incorrect. http://home.deib.polimi.it/gatto/WarmingAndDiseaseRisk.pdf Several recent studies have shown an expected increase in disease due to biodiversity loss, as it is typically pest species that fill the niches opened from local and total extinction. In truth I cannot say that I have ever read a peer reviewed article that says biodiversity is a  solely negative thing, and if I did I cannot say that I would put much faith in what it had to say. To view it from an anthropocentric viewpoint makes no sense as we should be surviving with local species, not by destroying the environment. 

I feel like the answer you may be looking for though is in production of monocultures vs polycultures. Many of our high productivity monocultures do indeed have a higher productivity than our most diverse polycultures, but that is not synonymous with diversity being negative. High productivity is not a strong measure of ecosystem value.

Your question is incomplete as biodiversity is not the matter of negative or positive effects in a community or ecosystem. Because biodiversity is the totality of interacting or resident organisms/species in a spatially defined site or unit. You do not want to be confused with species diversity or ecological cohorts with biodiversity that includes all those you are asking about.  Yes, any adventive or ecological cohorts like predators or parasites could make either negative or positive effects dependent on the state and composition of the biodiversity of a spatial target community.

Thanks for this answer, Michael. I do not claim that biodiversity is "solely negative", quite the contrary, I actually believe that it is valuable and essential to human well-being. I don't agree, however, that it has no negative impacts on humans. The paper to which you've provided the link is interesting, but rather specific, so I would not generalise...

I have the heavy impression that anthropocentrism is heavily misunderstood by many here. I can only direct your attention to the link I embedded above.

The productivity issue does not convince me either, and is not really what I am looking for. But thanks nevertheless.

Dear Bartosz, Humans are top consumers and as such predator-prey systems are a good example. Removing other species from a diverse system can increase individual predator efficiency through the elimination of negative effects from presence of non-prey or intra-guild predators or competitiors. This may result in negative relationship between species richness and performance of individual consumers (e.g. humans). A typical result is destabilisation by overexploitation where predators will more likely annihilate themselves than in species rich systems. Hence, when you consider co-existence/stability, diversity will have a positive effect. If you ask a question, what the effect of diversity is on sustainability (co-existence) in the system, then it is a positive effect.

Michael, the polyculture is an interesting example, but I would argue differently. Monocultures convincingly produce more when there is heavy nutrient and pesticide input only, and crop combinations may be factitious, hardly comparable to natural communities. Also, pest pressure is expected to be lower in polycultures as a result of diversity effects so under low nutrient input, polycultures may be more productive. Again, as one of the oldest studied systems, tons of literature is present on the topic but I would look into results of the long-term biodiversity epxeriments too.

Dear all! I just couldn't resist from giving an addition to Ferruccio's last answer! I am very much sure that the magnitude of species diversity is not only non-harmful to humans - it is also the prerequisite for our long term survival.

Let me add one more thing: I strongly think that the best anthropocentric way of our behavior is exactly the ecocentric way - simply because it may serve best our civilization in its long term survival right here in this planet!

An interesting question, although one that, I suspect, will have little support. Our destruction and degradation of biodiversity is wanton and not reciprocated to any quantifiable degree. Flippantly, in a temperate forest a falling tree may kill a human, as may a toxic mushroom, a rampaging bear... - certainly a negative effect on individuals! Of course you can argue for malaria, ebola and their vectors as examples. But remember that the cures are derived from biodiversity too. E.O. Wilson sums it up very eloquently in The Diversity of Life (p.331)"Humanity coevolved with the rest of life ... it is reckless to suppose that biodiversity can be diminished indefinitely without threatening humanity itself." 

You mention mercury in fish, and bioaccumulation to levels toxic to humans. This is possible through natural biogeochemical processes, but there are also prevalent anthropogenic routes for example as by-products of gold mining. We're the problem!

Thanks Julian. Only one short comment: you write "But remember that the cures are derived from biodiversity too.", which is conventional, but nevertheless not really true wisdom. Most drugs nowadays are developed through rational drug design or extracted from a few domesticated species.

Dear Bartosz, I really recommend you the book of Simon Levin: "Fragile Dominion: Complexity and the Commons". There is a lot in there on how ecosystem services may be derived from species interactions and diversity. It also places your original question in context, like possible negative effects of biodiversity in temperate forests on human well being? I think there is an example in there (read book many years ago), that of Catskill mountain and the drinking water of New York. As far as I know they began converting lands into farms and the drinking water supply of the city became endangered. It was a much more financially feasible plan to convert the farmland back into nature, than establishing monstrous drinking water facilities for the city.

And this is my whole problem with the approach these negative correlations (not effects!) insinuate. Depending on a local financial situation, policy makers would designate an ecosystem service negative (say cattle production is negatively correlated if a land is forest), so let's destroy the land, but at the same time willing to completely ignore another much more important service:  drinking water, for the sake of instantaneous profit.

Also, saying in your original posting that high mercury concentrations in tuna are the result of negative effects of biodiversity, is "putting the carriage before the horses". You could argue the same for DDT accumulation in long food chains, but we all know that you cannot blame biodiversity for that!

The same view shines through your above comment on medicines. Of course they can synthesize a lot of chemicals for medical purposes and in a much more purified state. But tell me, where were many of these chemical compounds discovered and isolated in the first place? We get endless source of inspiration form natural ecosystems. And isolating these compounds from crops is not the same as natural plants, because they are under artificial selection, and actually crops are often selected against containing these chemicals because they give undesirable properties (like bitter taste)  to plants. In this context I can paraphrase Carl Sagan by saying that destroying nature for profit is like a farmer, who eats (or sells) all the corn including that needed for sowing next year...

Rational drug design is not based on compounds found in nature, not in a specific sense at least. It's rather deducting possible effects of chemicals on physiology based on our knowledge of how these chemicals are structured. You don't necessarily need nature for that, at least not in a farther-reaching sense than that chemistry has developed by studying chemical processes in nature (where else?).

I meant domesticated animals, not plants, as source of medicines. But that's not the point. The point is actually that we are moving ever farther away from the question I posed in the first place. I understand all of your concerns and actually share many of them. Still, for my work I need the question above answered and do think that it makes sense.

Bartosz, your question makes very little sense from an anthropocentric point of view because you implicitly exclude humans from your biodiversity set. Your examples highlight that. Heavy metal concentration in high trophic level predators is not a negative impact on any species other than to the ones in which the metals are concentrated. If it is a problem for humans, it is because some societies consume high trophic level predators at unnatural rates, coupled with the fact that most of the problematic metal concentrations are derived from anthropogenic pollution. Futhermore, there is no doubt that the impact of pathogens on human societies are exacerbated to the extreme by overpopulation, poor sanitation and health care systems, and increasingly by terrible agricultural practices and relentless domestication of wild spaces (which harbour novel pathogens). Now, if you include humans explicitly into your biodiversity set, perhaps your question would make a bit more sense. Humans then would suffer from the same antagonistic interactions to which all species are subject, namely predation, competition and negative mutualisms (e.g. parasitism). I can think of no instances where modern humans have not successfully subjugated wild species to be on the losing end of those interactions, with the exception of the anthropogenically-exacerbated situations mentioned above.

Peter, thanks for the valuable comment. Actually, I oppose the (explicit or implicit) exclusion of humans from nature, so I agree with your points that it certainly is not a unidirectional relationship. Sometimes ecosystems function just as feedbacks exacerbating our harmful actions (such as emissions of mercury). Perhaps I should have made the purpose of my question clear in the first place: I am going to conduct a questionnaire-based (economic) valuation study of biodiversity. And I would like to include many different aspects of biodiversity's contribution to well-being. So far, all of them are positive. But I think that, even though one may often argue that its "our own fault" when there are negative effects, they should nevertheless be included in a study like mine.

That makes sense Bartosz.  I would, however, be very careful of how the questions are framed to the responders. Perhaps try to make a clear distinction between ecosystem effects that are independent of human action versus those that are either exacerbated or initiated by human action?

That's a nice idea, thanks very much.

Dear Bartosz: I am not sure what the core of your question is. Biodiversity is not by itself harm to humans but rather the other way around.  Humans are the primary cause of the biodiversity loss which is in reality destroying the foundation of our life-support system.  Biodiversity is not the product of humanity but rather inclusive of humans as a species.

Answer to your question would emerges if you critically understand and define what biodiversity is and what you mean by "species diversity." Biodiversity refers to the totality of all interacting living organisms/species in a spatially defined site or unit that sustain the functionality of our life-support system. That is the product of long evolutionary process but not the human's commodity or resources for no avail.

The definition of biodiversity I find most useful is "multiplicity of kinds within biotic or biota-encompassing categories" (by Donald S. Maier). I do not find useful the idea that biodiversity is "the totality of all interacting living organisms/species in a spatially defined site or unit that sustain the functionality of our life-support system". I focus instead on the diversity/variability issue, without paying much attention to the individual species/genes/whatever that make up biodiversity.

Dear Bartosz,

I fully agree with Ke Chung Kim!

Regardless of any opposing reference(s) I really cannot support the view where biodiversity is merely the multitude of "kinds" by itself! Everyone should by all means rely on valuable references but is highly recommended that a scientist rethink by himself about the things that are written. Every current biodiversity exist and have been existed thanks to the interaction (totality of species functions) and therefore biodiversity cannot be viewed without considerations of the total interaction between the species! Biodiversity is crucially a system of different "kinds" (species/genomes) in a given space and time interconnected with highly complex network of interactions.

Dear Neven,

what you are writing about is in my understanding better described as "nature", not "biodiversity". Otherwise the latter term would be superfluous. That's why I find it useful to use a narrower definition than is common in conservation debates. Based on this narrower, analytically more exact definition I analyse one specific aspect of what you might broadly term "nature". I do not claim that this is all nature is about. Interactions, evolution etc. are important as well, but if I would include them in my definition, it would cease to be analytically tractable.

Thank you Bartosz, for clarification of your views. But, I can equally argue with the very terminology: we have a term "richness" that could apply to a nude number of species or any other entity on a given area without any attributable function(s) and "biodiversity" to apply to a species diversity in its full biological (ecological) sense. I would therefore suggest the distinction between the „species richness“ and „biodiversity“. Species richness is simply a count of species and perhaps a term you are looking for.

The concept of biodiversity as the foundation of life-support system including all living organisms/species is fundamental to answering your rather confusing question "What are negative effects of biodiversity in temperate forests?". If that is not resolved in your mind, you should modify your question little more specific concerning forest management. By definition temperate forest refers to biodiversity of temperate forests inclusive of all tree species along with all other living things, perhaps including forest-dwelling humans. Negative effects to biodiversity rather than by itself to "forests" are caused by humans and their needs and anthropocentric application.

Dear Neven,

the problem with richness is that it is only about species richness. Biodiversity as defined above is about "richnesses" of many different things "at the same time", so to speak.

Dear Bartosz, "What are negative effects of biodiversity in temperate forests?" is not well defined and not the matter of semantics. That, however, if it is referring to the core of negative effects to biodiversity, your answer comes down to humanity and thus human species, particularly "Homo sapiens  technophileae" at large and not limited to "temperate forests" but rather to the global biodiversity on the planet Earth. Then, your question should lead to what we are going to do about it unless we ultimately face extinction of human species.

The comments you have received should have shown you that this is a very weird question. I find it hard to grasp just what it is that you are looking for here. In a temperate forest context, it would be hard to pinpoint diversity as such as a detriment to humans, other than in the sacrifice of yield, as in a monoculture use. On the other hand the "normal" diversity of temperate forest may include organisms that impact adversely on human interests. For example, wild boar are now renaturalised  by accident in English forests, and are a nuisance to neighboring farmers. They may also constitute a danger. I guess this pinpoints where natural diversity in forests is negative: where it imposes burdens on human activity outside the forests themselves but near them.

However, it is equally the case that the explosion of deer in UK forests is an economic burden to both foresters and farmers. We can make the case that this a result of diminishing diversity by removing top predators.

I guess that it is the negative aspects of particular species that are a part of natural diversity, rather than diversity itself in any abstract or general way that might matter. But I am aware that I may have misunderstood the point of your question!

 Robert Cameron.

@Robert Cameron:

Thank you for your answer. Your examples of species having negative effects are not exactly what I am looking for. But maybe there are no negative effects of "diversity as such", at least not in temperate forests... Still, I've found your response quite useful, so thank you.