Are Milkweed and Monarchs Making a Comeback?


Everyone who knows about monarch butterflies, likes monarch butterflies. This blog post focuses on their food source -- milkweed. And to get you in the mood, here's an amazingly beautiful picture my friend Eniko made of a monarch:

In recent years, I had heard reports of the dwindling number of monarchs making the annual migration from the US to a small section of forest in Mexico. In 2013 the number of monarchs covered a record-low of 1.7 acres, but in December 2015 it was back up to 10 acres (still not the 44 acres they occupied a couple of decades ago, but certainly headed in the right direction!)

One of the causes of the declining number of monarchs is the loss of the plant that is their food source (and where they lay their eggs) -- the milkweed plant. As more and more land is paved over and built on, and as large farms get really good at killing all the plants that aren't the crop they're growing, the number of milkweed plants has declined. Thankfully there have been a few programs trying to increase the number of milkweed plants (both government and private projects), and hopefully that's helping the monarchs make a comeback!

So, if you were going to plant some milkweed to help the monarchs, what kind should you plant? The xerces page recommends planting milkweed that is native to your area. And this bonap page provides US maps showing the range of each different kind of milkweed. I perused their maps and found that common milkweed (asclepias syriaca) is native to North Carolina (where I live), so that might be a good one for me to plant. I clicked the thumbnail for that map (see screen-capture below) to see the full-size map:

Their full-size map showed more detail, but I still couldn't determine whether common milkweed specifically grows in my county. The county borders aren't quite detailed enough to easily recognize each county by shape, and the geographical area where Wake County is located is somewhere along the edge of the bright green and dark green counties.

In addition to not being able to determine the exact county in their map, there were a few other problems I noticed. For example, the full size map doesn't have a title showing what kind of milkweed is being displayed. The thumbnail had a label, but the large map did not.

And then there are the colors... Their color legend is so large and complex (see below) that they even put it on a separate page from the map. There are state colors (dark green, brown, etc.) and county colors, and then Mexico is gray (which is not in the legend). And some counties are even striped. I guess they're wanting to show a lot of information, but their use of colors seems a bit overloaded. In addition to their colors being overly complex, I think it's visually misleading to color a whole state, when just one county has milkweed (for example, see Texas in the map above).

So I decided to create my own simplified version of the map. In mine, I only shade the counties that have milkweed (not the whole state). And I put a nice straightforward title at the top of the page. My color legend is short/simple, and only shows the colors being used in this particular map. I also added mouse-over text so you can easily see the county names (click the image below to see the interactive version with mouse-over text). In my map, I can use the mouse-over to definitively find Wake County, and see that common milkweed is "present, and not rare".

common_milkweed

Sometimes simpler is better -- do you prefer the original map, or my simplified version? What other recommendations do you have that might make the map even better?

(Oh! - And don't forget to check out my monarch butterfly animation map in this previous blog post!)

This content was reposted from the SAS Learning Post. Go there to read the original.

Robert Allison, The Graph Guy!, SAS

Robert Allison has worked at SAS for more than 20 years and is perhaps the foremost expert in creating custom graphs using SAS/GRAPH. His educational background is in computer science, and he holds a BS, MS, and PhD from North Carolina State University. He is the author of several conference papers, has won a few graphic competitions, and has written a book calledSAS/GRAPH: Beyond the Basics.

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Re: Colors on a map
  • 9/12/2016 5:29:17 PM
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..

Kq4ym writes


 I've been thinking lately about the destruction of mosquitoes here in Florida over the Zika fear. It would seem to me that although the authorities are in agreement there's no danger to insecticide sparying to humans, I do wonder what it's going to do to the environment and those creatures like butterflies and more, who have to survive the spraying.


 

Put dangerous chemicals like pesticides in the hands of dingbats, and you won't have to wonder anymore about the potential environmental impact ...

South Carolina Accidentally Kills Millions Of Honeybees With Zika Spraying


It was quieter than usual in parts of Dorchester County, South Carolina on Monday. Silence had replaced the familiar buzz as millions of the usual noisemakers lay silent on the ground — dead.

It was an unanticipated massacre, collateral damage in the war against the Zika virus.

County officials had been targeting mosquitos when they blanketed a 15-square mile area with pesticide on Sunday. But they ended up killing at least 2.5 million honeybees as well.

"It was like visiting a cemetery, pure sadness," wrote one woman who walked through an affected apiary on Monday.


 

Oops ...

 

Re: Colors on a map
  • 9/12/2016 11:42:27 AM
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Yes, I think simpler is better in most cases and a simple mouse over of the areas of interest does that well. I've been thinking lately about the destruction of mosquitoes here in Florida over the Zika fear. It would seem to me that although the authorities are in agreement there's no danger to insecticide sparying to humans, I do wonder what it's going to do to the environment and those creatures like butterflies and more, who have to survive the spraying.

Re: Milkweed to the rescue
  • 9/11/2016 6:59:05 PM
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I was happy to see a monarch today, as I was taking my outrigger canoe out of Lake Crabtree (just across I-40 from the RDU airport). :)

Milkweed to the rescue
  • 9/11/2016 5:30:21 PM
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..

Robert writes


... I think it's visually misleading to color a whole state, when just one county has milkweed (for example, see Texas in the map above).


 

This, plus the map showing just one tiny county in the Texas Panhandle with milkweed to support monarch butterflies, got me agitated, since I knew that Central Texas hosts a gigantic population of monarchs at the right time of year ... and I figured something was wrong here, or all my beliefs about monarch butterflies in Texas were based on illusion or something. As a result, I have learned more about monarchs and milkweed than I ever thought I would want to know.

As Robert's article states, he has mapped just ONE species of milkweed, whereas there are at least more than twenty. And Texas hosts several milkweed species. In fact there is a state-sponsored effort (in Tea Party Texas, go figure) to increase monarch habitat to compensate for all the milkweed being destroyed in Mexico by agricultural foliage-clearing operations.

Central Texas in fact is a major waystation in the migration pattern of monarchs, as you can see in the following map:

 

Here's a photo of a monarch recently flittering among the Swamp milkweed along the Llano River here in Central Texas:

 

So, while Texas doesn't seem to be a prime host for the Asclepias syriaca variety of milkweed Robert enjoys there in North Carolina, it has its own varieties which are quite nourishing to all the cuddly little monarch larvae (see photo below), thank you very much.

(For more on the exciting topic of monarch butterflies in Central Texas, see: Llano River: Late season nectar plants await Monarch butterfly migration.)

 

Re: Colors on a map
  • 9/7/2016 2:12:43 PM
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I didn't know the species was so reliant on one single plant.  I will have to encourage my gardener friends to plant milk weed to help the Monarchs out. 

Re: Colors on a map
  • 9/7/2016 11:32:52 AM
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Simplicity is almost always the right choice... so yes, bravo to the 3-color limit here. And to more insight to what's driving one of the most interesting and beautiful migrations of the natural world.

Re: Colors on a map
  • 9/6/2016 1:37:34 PM
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Thanks guys! - I'm sending Eniko a link to your comments & compliments!

Re: Colors on a map
  • 9/6/2016 1:13:46 PM
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@Robert

And please relay to your friend that this monarch photograph is perhaps the best I've ever seen in any of your blogs.

Re: Colors on a map
  • 9/6/2016 1:13:21 PM
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@Robert I agree that simpler is better. Kudos to your friend's photography skills. It's difficult to capture butterflies well as they don't sit still very long with their wings spread. I once caught a shot of one at Bayard Cutting Arboretum, but it's not nearly as clear.

 

Re: Colors on a map
  • 9/6/2016 1:08:42 PM
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"Yuck" is a good word for it! 

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