Seed Sourcing Strategies for a Changing Climate

Years ago, I wrote a blog post comparing prairie restoration to the rebuilding of a city after a major disaster.  I was making the point that our objective with prairie restoration shouldn’t be to create something that looked like it used to or even like the prairie next door.  Instead, we should focus on restoring function to a landscape that had been fragmented and thus degraded.  I ended the post with this sentence, “After all, we’re not building for the past, we’re building for the future.”

I still stand by that, though my thoughts continue to evolve as I learn more about the challenges facing prairies in today’s landscape.  In most places, prairies exist as small and isolated fragments where species and their communities are fighting to survive threats invasive species and other major challenges.  Because the fragmentation of their landscape, many of those species are fighting without the hope of reinforcements from elsewhere.  They’re simply fighting with the troops and ammunition they have on hand. 

Restored prairies don’t have to look a certain way to be effective. In most cases, they should be judged on how well they help stitch a prairie landscape back together. Plant diversity is a key component of that, of course, so restored prairies have to be built and managed so they can sustain that diversity, even as the climate changes.

The rapidly changing climate adds additional stress to those troops by changing the battle conditions – often favoring the enemies.  Many of us have placed hope in the idea that the genetic diversity within species in local prairies will be enough to allow them to adapt and keep fighting.  That’s a big assumption.  What if they’re not equipped to survive a long-term shift in temperature and precipitation conditions? 

If restoration is supposed to bolster the function of fragmented landscapes, how can we best design strategies that decrease stress on isolated prairies and facilitate their need to adapt to changing climate?  For a long time, most of us have stressed the importance of using locally-harvested seed to ensure the plants we grow in restored sites will be adapted to those sites.  In the face of climate change, some have wondered if we should go further afield and gather seeds from places that have the kind of climate that is projected for our restoration sites.

That ‘climate matching’ strategy has some obvious flaws.  If we venture southward, for example, to find plants living under the climate conditions we think will prevail in our restoration sites, those plants will likely to be adapted to different soil types, soil textures, and photoperiods.  Plus, what if today’s climate models are wrong and the future climate is different from current projections?

Here are three photos of prairie larkspur (Delphinium carolinianum) from – left to right – Texas, Kansas, and Nebraska. All three of these photos were taken within a few weeks of each other in 2019. They are all the same species but grow under very different climate conditions.

And yet.  The climate is changing and those isolated armies are already struggling.  If we’re going to provide them with reinforcements and help re-connect currently isolated sites, we want to make sure we recruit the best soldiers we can.  Harvesting local seed just brings in more of the same local genetics we already have.  Climate matching might bring in genetics that won’t fit local conditions.  What do we do?

Fortunately, a team of ecologists led by The Nature Conservancy’s Marissa Ahlering is conducting some experiments that might help solve the conundrum.  Over the last 2 years, they have begun studying the concept of a ‘regional admixture’ approach to prairie restoration seed mixes.  Below, I interview Marissa about the research and what it might mean for the future of prairie restoration.


PE: First, can you briefly describe your position with The Nature Conservancy?

MA: I am the Lead Prairie Ecologist in Minnesota, North Dakota and South Dakota. The simplest way to explain my job is that I bring science to bear on our grassland conservation issues for the region. Sometimes that means taking the science that exists and applying it to our conservation challenges and sometimes that means collaborating with others to do the science that is needed to fill our knowledge gaps so that we can move our conservation work forward faster.

Marissa Ahlering. Photo by Cara Byington

PE: What do we know about the amount of genetic diversity within plant species living in prairie fragments?  Is it a pretty sure bet that those species are underequipped to deal with climate change?

MA: Honestly, not a lot. Information on genetic diversity and adaptive capacity is lacking for nearly all our native plant species. Work has been done with a very small handful of common prairie plants (e.g., switchgrass, big bluestem, purple prairie clover, and Echinacea angustifolia). For these species, more genetic diversity was found within populations than between populations, and populations closer together are more similar than populations farther apart. This is typical for species with large geographic distributions. Most of this work has been done using parts of the DNA that are not important for the functioning of the plant, so it is somewhat unclear what this means for the adaptive capacity of these species. Genetic techniques can now consider variability across the entire genome and look at parts of the plant’s DNA that might have relevance to characteristics that will help the plant survive better or produce more seeds. In short, there is still a lot to learn, but based on some general principles of population biology and ecology, there are reasons to be concerned.   

Prairie loss and fragmentation have disrupted the population biology of plant species to varying degrees across the Great Plains. Plants maintain genetic diversity with gene flow, and gene flow happens through the exchange of pollen and the movement of seeds. Dispersal patterns for both pollen and seeds have been disrupted by this prairie loss. The now isolated patches of prairie can no longer exchange pollen or seeds and, therefore, genes. However, most of the plants in our prairies are long-lived individuals. Why does this matter? The persistence of long-lived individuals could mask or delay the eventual impact of reduced seed and pollen dispersal.

I certainly don’t think it is a sure bet that prairie plant species are ill-equipped to deal with climate change, and I also think we can use some general knowledge about population genetics, population dynamics, and life history characteristics to identify populations or species that might be more at risk. Factors that are likely to predict which species will be at risk of reduced genetic diversity, fitness, or adaptive capacity are degree of isolation, population size, mating strategy, and possibly dispersal strategy. For small, isolated sites it is a pretty sure bet that dispersal of new individuals/genes into the site is going to be much more limited. From studies in many other species and ecosystems, we know that generally reduced population sizes decrease genetic diversity. Plants have many different mating systems, and there is some evidence that species that have to mate with other individuals are more prone to genetic diversity loss. Finally, there is also some evidence that insect pollinated species are less likely than wind pollinated species to have gene flow among isolated populations. 

Harvesting Maximilian sunflower seed from a remnant prairie about 6 miles from where it was later planted. We can be confident the plants growing from those seeds will be well-adapted to the site. But will those plants still be well-adapted fifty years from now?

PE: What is the ‘regional admixture’ approach and the case for testing it?

MA: Good question. These terms get used in many different ways. Seed sourcing strategies vary by how far seed comes from and number of different sources used. On one end of the spectrum is a strictly local single source strategy, and on the other end would be a predictive strategy where seed is obtained from sources currently experiencing future conditions. Depending on the models used, predictive sourcing, sometimes called climate-matching, may require seed from fairly long distances. A regional admixture approach falls somewhere between these two extremes. Our approach to this has been mixing seed from multiple geographically close and/or intermediate distances from the restoration site. For our current project, we did not use a specific distance cutoff, but seed was obtained from sites ~5-50 miles from the restoration site. This approach tries to account for local adaptation while increasing adaptive potential.

All seed sourcing strategies have tradeoffs in their risks and benefits. On the strictly local end of the spectrum, it is highly likely seed will be adapted to the current conditions of the site. However, the risk of reduced genetic diversity and adaptive potential is higher, as well as the risk of inbreeding depression. Inbreeding depression occurs when closely related individuals mate resulting in decreased genetic diversity and reduced seed production or plant survival. When fragmentation reduces population sizes, this can alter mating patterns and increase the relatedness of nearby individuals. The current status of inbreeding depression in remnant plant populations is largely unknown. It has been detected for small, isolated populations of Echinacea angustifolia, and decreased survival and/or offspring from inbreeding depression is a well-documented phenomena.

On the predictive sourcing end of the spectrum or sourcing from many different distances from the restoration site, the benefit is high adaptive potential and ability to deal with future conditions. However, the risks here are threefold. The first is if future conditions do not yet occur at the restoration site, initial establishment might be challenging. The second is that environmental factors might be quite different between sites very far apart, which could lead to maladaptation. The last is the risk of outbreeding depression. Outbreeding depression is essentially the opposite of inbreeding depression, when plants produced from the mating of two distantly related individuals have reduced seed production or survival. Contrary to inbreeding depression though, the results of outbreeding are not always negative. Sometimes when distantly related individuals mate their offspring actually do better than their parents. This can especially be true if the parents come from populations with low genetic diversity that is already experiencing inbreeding depression. The challenge with outbreeding is that both outcomes (positive and negative) have been observed in various species and situations so generalizations about the effects of outbreeding are difficult.

We chose a regional admixture approach to balance the benefits and risks. The approach of mixing multiple seed sources locally or regionally captures some of the benefits of local adaptation, increases adaptive potential, and reduces the greatest risks of outbreeding by not sourcing seed from too far from the restoration site. The negative consequences of inbreeding depression are clear while the negative outcomes for outbreeding are less certain, and we reduce the risk of outbreeding depression by not sourcing seed from long-distances.

Many of the seeds being mixed here were harvested locally in our Platte River Prairies, but we also travel into adjacent counties, and sometimes a little further, to find seed.

PE: Is this something you think others should be using now or do you see it more as an experiment and suggest people should wait for the results of your work before implementing it at a large scale?

MA: This approach has been widely recommended in the scientific literature. We have now implemented it across over 900 acres of TNC restorations in Minnesota and the Dakotas. We did set up test plots to evaluate the success of this approach. Obtaining seed from many different sources for all species in a seed mix is extra work in an already time-intensive process, and we wanted to evaluate the impact on outcomes. However, the results from this study won’t come for many years and the effects of climate change and habitat loss are being felt by our prairies now.

I think people need to weigh the pros and cons of the different seed sourcing strategies for themselves and their restoration context. The plea I will make is to make sure you consider the pros and cons of your business as usual seed sourcing strategies as well. All of our actions have risks and benefits, including the use of locally-harvested seed from the site right next to your restoration. Strictly local seed is not without its own drawbacks and risks, and those should be considered alongside the risks and benefits of a new approach.

PE: What else do you want people to know about what you’re working on and what it means?

MA: Connectivity and maintaining large population sizes are generally considered to be the key for species to maintain genetic diversity. In places where connectivity and large populations still exist, mixing of seed sources is likely less of a concern, but in these settings, restoration itself is probably less needed as a conservation strategy. In the fragmented landscapes with limited connectivity where we are doing most of our restoration work, the issues around loss of genetic diversity and the need to boost adaptive capacity in restorations is greater. We are currently using this regional admixture approach to balance the tradeoff between inbreeding and outbreeding depression while increasing genetic diversity and adaptive capacity. Where we ultimately need to get to in the Great Plains is climate informed seed transfer guidelines that incorporate both local adaptation to current condition and adaptive capacity for the rapid pace of climate change. The genomic, modeling, and spatial ecology tools exist to achieve this. We just need to put them to work.

PE: Thanks, Marissa, for all of this thought-provoking information. If anyone would like further information, check out the links below:

Short video on the Prairie DNA project Marissa describes above.

A recorded webinar on this topic.

Hubbard Fellowship Blog- Building a Volunteer Program

This post was written by Evan Barrientos, one of our Hubbard Fellows.  Evan is a talented writer and photographer and I encourage you to check out his personal blog. If you would like to see more of his photographs, you can follow him on Facebook.

When I started my Fellowship I had strong interests in outreach and stewardship. I was hoping the Fellowship would help me choose which to focus on, but instead it’s shown me a way to combine the two: volunteer stewardship programs.

Although I greatly enjoy the physical work of stewardship and recognize that conservation can’t happen without it, I sometimes feel that it’s a losing battle. The fact is, the conservation movement just doesn’t have the resources to rigorously manage entire landscapes. Here on the Platte River Prairies, there are always more invasives than we can spray, more seeds than we can collect, more equipment repairs than we can fix, etc. This is why outreach matters to me. I think that in order for conservation to be successful we need to inspire more people to support it. Over the course of my Fellowship, I’ve come to believe that volunteer stewardship programs can make significant gains on both of these fronts.


Volunteers help collect seed from one of our larger Platte River Prairies.

Last June at the start of my Fellowship, I heard that there was a volunteer workday coming up. During high school I enjoyed volunteering at my local nature center, so I thought I would check it out. Although only three volunteers attended, at the end of the morning I sensed a hint of accomplishment and camaraderie. I decided I would stay involved with the workdays.

Only three more workdays had been scheduled for the year. Through a mix of chance and initiative, I wound up leading them. This was new territory for me and I would become very nervous for the entire week before each one, but the feeling of accomplishment afterwards was incredible. Not only did we accomplish large tasks in short amounts of time, but I sensed that people were learning a lot and building meaningful connections to our prairies. Little by little, new volunteers started showing up, people consistently drove from 1.5, 2.5, and 3 hours away, and my pre-workday nerves started to lessen.

I decided to extend the workdays into the winter. Although this meant figuring out a new volunteer activity (invasive tree removal), I felt that there was too much good momentum to quit. At this point I had started interviewing other volunteer coordinators for advice, and a repeated recommendation was to build a sense of community through social events.  Copying a great tradition from my high school nature center, I started hosting lunches after the workdays. People really seemed to enjoy these and the tree removal, and our average attendance grew to about nine. (In a later post I’ll summarize my findings from nine interviews and 160 responses to a survey I conducted).

With momentum still rising, in February I decided to attempt a larger event. Our ongoing prairie restoration was due to be seeded and I thought it would be a fantastic opportunity for volunteers to create something beautiful, important, and permanent. Some volunteers could even have the gratification of knowing that they had picked the seeds during the previous summer. I sent press releases to four newspapers, announced the event to the Nebraska Master Naturalist program, invited members of a local church, recruited TNC staff to attend, and advertised a large potluck. Despite freezing temperature and 25mph winds, 30 volunteers (probably the largest volunteer event we’ve ever had) came to help! We made tremendous progress very quickly, and then enjoyed a delicious potluck and Q&A with our staff. The event was covered by a local newspaper, picked up by the Omaha World Herald, and even mentioned in USA Today!

New people of all ages continue to attend the workdays, as well as several who have been coming regularly since the summer. Among our most dedicated volunteers are a college student, a father/son team, and a grandfather. Since June, 48 volunteers have contributed 270 hours of stewardship. This time is so valuable because it is spent on essential tasks that wouldn’t receive any attention otherwise. Tree removal is a great example. If we let trees go wild on our prairies, very soon we won’t be able to hay, graze, or burn the prairies the way we need to to meet our management objectives. Yet in my 11 months here I’d estimate that staff have spent less than ten hours treating young trees, simply because we’re busy with more specialized tasks like prescribed fire. Fortunately, volunteers have contributed 105 collective hours to remove trees from 70 acres of heavily-infested prairie since November.

But workdays are even more valuable, in my opinion, because they provide a way for people to make personal connections to our organization, Nebraska’s prairies, and global conservation issues. By attending workdays, volunteers learn about prairie ecology, management, threats, and more. By spending time in our prairies and working towards a goal, they develop a personal attachment to our properties and to prairies in general. And who knows, maybe the workdays will even inspire some to dedicate their careers or savings to conservation. That’s what I love most about leading workdays: you never know when you’ll change someone’s life forever. Sound far-fetched? Well, that’s how I got here.


The last aspect of building a volunteer program is sustaining it. The volunteers have asked me many times, “What will happen to the workdays after you leave?” I think about that a lot. My goal from the start was to foster a group of volunteers with enough dedication and experience to be fairly self-sufficient after my Fellowship ends. So far, I’ve trained two dedicated volunteers to lead workdays. I’m hopeful they’ll continue to engage Nebraskans in the meaningful work going on here after I’m gone. Based on the enthusiasm I’ve seen so far, I’m optimistic that they will.


Steve (blue sweatshirt) has attended 7 of the last 11 workdays, and has stepped up to become a Workday Leader! He’ll be leading his first workday this Saturday!

If you’d like to get involved, our next workday is this Saturday, April 23, at 9:00am at the Platte River Prairies. Email to sign up!