This is a big question...
And this caused me to do a lot of research over the past week. I did SO much that I'm a bit late in posting my answer. I'll talk about this later in this post, but I wanted to let you know that I haven't forgotten about this SRS post--I just got a bit caught up in it all!
But first, our Challenge for the week:
How healthy IS the Mediterranean?
That's a bit like asking "how healthy is Europe?" The two problems are similar--the entity in question is a bit ill-defined (is Russia part of Europe?), it spreads over a huge area, it varies tremendously from place to place (the coast of Monaco is nothing like the coast of Egypt), and what do you mean by "healthy" anyway?
Here are four side-by-sides of different Mediterranean coastlines that illustrates my point. Note how much difference there is in the level of human activity, and in the surrounding ecology of the coastline. The coast varies from deep desert, to scrublands, to forests. Some are shallow and mild, others are deep and wild. It is a highly variable place.
|Four side-by-side sections of Mediterranean coastlines
If you look at the Mediterranean as a whole, you see the scale of the Challenge. What does it mean to ask about the "health" of a body of water that's 2,500,000 square km (970,000 sq mi) with 3,750,000 cubic km (900,000 cu mi)? Any kind of answer will have to involve multiple countries and their data.
|The Mediterranean from Google Earth. Note the relatively shallow waters east of Italy,
south of Sicily, around the Greek islands, and the basins of deeper waters.
|The crystal clear Aegean... is it TOO clear?
But that one dive made me think: Is this really the "normal" condition of submarine life around Greece? What about the Mediterranean more generally?
To repeat this week's SearchResearch Challenge:
1. How healthy IS the Mediterranean? Are there still places where one could go diving and see a rich, healthy, submarine Mediterranean ecosystem that's full of fish, invertebrates, corals, and other marine organisms? Where should I go to have this experience? (Note: Anything outside the Straits of Gibraltar, or the Bosporus Strait, or doesn't count.)
More generally, I'm interested in what condition the Mediterranean is in these days. I'm also interested in how much the Mediterranean has changed over the past 100 years. Has it always been like this? Or has something changed recently?
There are many approaches to a Challenge like this. For instance, you could collect data from many different points around the Sea and compare/contrast pollution levels, historic fishing rates, and so on.
But since we have limited time, perhaps what I'm looking for is an authoritative summary of different variables that define the ocean's health.
By looking at the map it's clear that trying to answer this question means looking at it from a trans-national point-of-view.
What does that mean from a SearchResearch perspective? Well, there are several different research strategies we could follow. Here are my top contenders:
1. Work from Wikipedia outward. That is, start with the Wikipedia article and see where that leads. Look at the articles that are referred-to, and then look at articles that those articles refer to, following the reference chain outward.
2. Find a trans-national organization's report. What would such an organization be? Perhaps the UN, or maybe an international oceanographic research organization.
3. Search through Scholar for scholarly reports. Find a few and see if there's a consensus.
4. Search through a respected scientific journal that covers ecosystem science. This is analogous to searching through Google Scholar, but focuses just on one journal's output on the topic.
Here's a summary of what I found following each of the strategies...
Strategy #1. Work from Wikipedia outward.
I searched in Wikipedia for [ Mediterranean ] which took me to the article for Mediterranean. In that article, there's an entire section called "Environmental history" which includes sections on biodiversity, pollution, overfishing, and aquaculture. That's a useful section to read, as it not only gives summaries of those topics, but also tells you what terms (e.g. "biodiversity," "overfishing," "marine debris," and "Lessepsian migration" or "Erythrean invasion") are useful when doing other searches on this topic. (This kind of additional terminological knowledge is useful when searching because there are so many web pages that include "Mediterranean diet" or "Mediterranean vacation" or "Mediterranean lifestyle" that it's sometimes hard to find good results!)
In summary, from reading the Wikipedia article I learned that the Mediterranean has been heavily used for the past 5,000 years, but the last 130 years have been a time of great change as fishing, pollution, and the opening of the Suez Canal have transformed its ecosystems. It seems to be severely overfished (more than 65% of fish stocks are below safe biological limits), and the number of pristine regions are very small.
One of the important functions of a Wikipedia page is to direct you toward other content that's useful on the topic.
I learned that there is ANOTHER Wikipedia page on just the oceanography of the Mediterranean Sea. While that particular page is rather short and un-useful, IT DID lead me to a 2010 paper on the "Biodiversity of the Mediterranean Sea: Estimates, Patterns, and Threats"  which says, in summary:
"...At present, habitat loss and degradation, followed by fishing impacts, pollution, climate change, eutrophication, and the establishment of alien species are the most important threats and affect the greatest number of taxonomic groups. All these impacts are expected to grow in importance in the future, especially climate change and habitat degradation. The spatial identification of hot spots highlighted the ecological importance of most of the western Mediterranean shelves ... western African coast, the Adriatic, and the Aegean Sea, which show high concentrations of endangered, threatened, or vulnerable species." (from the abstract)
Okay. That's sobering.
From the Wikipedia strategy I learned a bunch of useful search terms, and have an overall sense that the Mediterranean suffers from issues of species invasions, overfishing, pollution, and has suffered greatly over the past 150 years.
I also checked out the Wikipedia article in other languages (Italian, Spanish, and Greek), and learned from them that invasive species is a real problem, especially with the invasion of jellyfish, and the loss of some plant species such as Posidonia (a previously common sea grass).
Let's try the next strategy and see what we learn from that.
Strategy #2. Find a trans-national organization's report.
The first question here is "how do we find a transnational organization?" I admit that I didn't think it would work, but my first query was:
[ transnational "Mediterranean sea" ]
(Note that I quoted the phrase "Mediterranean sea" to avoid things like "Mediterranean cruise" or "Mediterranean lifestyle.")
That query actually worked pretty well! The first result is a comprehensive report, "Blue Growth in the Mediterranean Sea: The Challenge of Good Environmental Status," which is a fairly large report by the World Wildlife Fund (WWF) that takes a comprehensive look at the development trends and status around the Mediterranean. This report summarizes data and comments from 8 EU Mediterranean countries (Croatia, Cyprus, Spain, France, Greece, Italy, Malta, and Slovenia) and gives a pretty decent analysis of what's currently happening and what the prospects are. They're a pro-environment organization, but the report seems to give a fairly balanced analysis of development and environmental factors at work.
While acknowledging that energy and development factors are going to happen, they comment that:
"It is likely that some pressures and, more importantly, cumulative impacts on marine ecosystems generated by the increasing exploitation of the sea will grow at a faster rate than the solutions developed and implemented to mitigate them..."And that,
"Consequently, there is a high risk of failing to achieve Good Environmental Status in the Mediterranean Sea by 2020 for 7 out of 11 of the descriptors of the Marine Strategy Framework Directive..."This report also shows the area around Greece (including all of the islands) as the most intensely fished region in the entire Mediterranean--which might explain some of the paucity of fish I saw in Crete.
It's another negative vote, but the strategy actually worked. (If you're interested, I recommend this report to you--it really is interesting.)
This SERP also returns a number of other reports by transnational groups, ("Mediterranean Endangered: For a sea free of waste"and "MEDTRENDS – Future Trends in the Mediterranean Sea: Duration 01/07/2014 – 30/06/2015" -- all of which concur with the pessimistic assessment of the future of the Med.)
Strategy #3. Search through Scholar for scholarly reports.
This is probably the simplest, most obvious approach--when you want authoritative, scholarly results--using Google Scholar is a fast way to get to this kind of information.
My query to Scholar was:
[ Mediterranean Sea biodiversity assessment ]
The SERP looks like this:
Note that each of these results is a paper published in journals like Marine Pollution Bulletin, Frontiers in Ecology, Conservation Biology, and Global Ecology and Biogeography. These are pretty serious papers that are sometimes fairly dense--but incredibly useful if you can slog through the writing.
It won't surprise you to learn that all of these scholarly papers say essentially the same thing: The Mediterranean is seriously overfished, subject to lots of invasions of different species (from foreign ships as well as imports from the Red Sea via the Suez Canal), suffers from pollution of many different types, and just plain overuse. The number of marine reserves is very low (too little to do much repair to the ecology). It's a very stressed ocean. (See  and  below as examples of this kind of scholarly work.)
Strategy #4. Search through a respected scientific journal that covers your topic.
A variation on the Scholar search is to select a particular general coverage science journal (that is open to Google Search) and do a search through that journal's coverage. I tired this method on a couple of journals like this and terms that I'd picked up from earlier reading (e.g., from the Wikipedia articles):
[ "Mediterranean sea" "Lessepsian migration" site:sciencedirect.com ]
[ "Mediterranean sea" biodiversity site:sciencemag.org ]
[ site:sciencemag.org "Mediterranean sea" fish stocks ]
Using this "search through a journal" method, I was able to find several journal articles that are excellent overview summaries. For instance, the first couple of results from the 3rd query above tell me that...
"They found that 64% of the unassessed [fish] stocks are below their sustainable numbers—comparable to the below-sustainability estimate of 63% for assessed stocks reported in Science in 2009. The findings indicate that unassessed stocks, such as cod and miscellaneous coast fish, are in decline—and are in particularly poor condition in developed areas like the Mediterranean Sea." 
"...scientists evaluated the status of more than 1200 species native to the Mediterranean Sea, the Black Sea, the Baltic Sea, the North Sea, and the European part of the Atlantic Ocean. Although conservation measures have been successful in improving stocks for some species.... The populations of more than 90 other species have plummeted low enough that they could go extinct, the report warns." This is confirming what we found via our other methods.
Now, in an ideal research process, I'd search for disconfirming evidence, which in this case would be articles about how the Mediterranean is actually healthy and doing quite well.
I did this using the "search through a journal" method, running queries like this:
[ site:nationalgeographic.com "Mediterranean sea" "healthy ecosystem" ]
(Here I chose National Geographic as a popular journal with a good reputation for writing about ecosystems.)
Using this "search for the disconfirming evidence" approach, I was able to find articles about the "healthy ecosystem" in the Mediterranean.
BUT, when you read through 10 or 12 of these articles, you'll find every single one of them has a dire assessment of the state of the Mediterranean:
“We found a huge gradient, an enormous contrast. In reserves off Spain and Italy, we found the largest fish biomass in the Mediterranean,” said National Geographic Explorer-in-Residence Enric Sala, the paper’s lead author. “Unfortunately, around Turkey and Greece, the waters were bare.” but ending up with a hopeful observation, usually like this:
"Fish abound in Spain’s Medes Islands Marine Reserve in the Mediterranean Sea. Unprecedented new research turned up healthy ecosystems in well-enforced marine reserves across the Mediterranean..."So I conclude that my search for disconfirmation has failed, and that the evidence is pretty strong that the Mediterranean is a deeply compromised sea with significant challenges.
Search LessonsIf you're still reading here, kudos to you! I know this is a long post, but this was a big, complicated question with some sophisticated methods.
In my research this week, I probably read 20 different articles (I've only given you the "top 6" citations below). This was not a simple Challenge--it took me probably 10 hours of research work. In truth, most people won't spend that much time, but the idea of taking multiple research approaches is a great idea. If you're locked into only one strategy, the lik
To answer this Challenge, I used four different strategies to search for information in very different ways. I did this in order to try and find very different resources that were on the topic. My hope was to find a good set of resources that would give me the ability to get multiple points-of-view.
So the Big Search Lesson of the week is that for complex research tasks, seriously take multiple approaches to the problem. See above for 4 different strategies, but it's incredibly valuable to look for your information in different ways (and don't forget to look for disconfirming evidence as well)!
And... for great diving in the Mediterranean, I found out that marine reserves (especially in Spain and Italy) are great places to go. That'll have to be my next trip!
 Coll, Marta, et al. "The biodiversity of the Mediterranean Sea: estimates, patterns, and threats." PloS one 5.8 (2010): e11842.
 Bianchi, C. Nike, and Carla Morri. "Marine biodiversity of the Mediterranean Sea: situation, problems and prospects for future research." Marine pollution bulletin 40.5 (2000): 367-376.
 Coll, Marta, et al. "The Mediterranean Sea under siege: spatial overlap between marine biodiversity, cumulative threats and marine reserves." Global Ecology and Biogeography 21.4 (2012): 465-480.
 de Vrieze, Jop de. "Netting Better Data on Global Fish Stocks" Science, Sep 12, 2012.
 Wilkinson, Allie. "Overfishing could push European fish species to extinction" Science, June 3, 2015
 Braun, David Maxwell. "Overfishing Leaves Much of Mediterranean a Dead Sea, Study Finds" National Geographic (online), March 2, 2012