July 29-230-Trish Long
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2019 SWCS International Annual Conference July 28-31, 2019 Pittsburgh, Pennsylvania
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July 29-230-Trish Long
- 1. Using a Land-use Change Analysis to Inform Wetlands Protections in New Jersey Trish Long / July 2019 USDA-NRCS
- 2. Wetland conversions in New Jersey Questions: • How many acres of wetlands in NJ were converted to agricultural uses since 1985? • Where are these conversions occurring? The Problem
- 3. I. Background II. Analysis III. Results IV. Conclusions and Next Steps Outline
- 4. Background Wetlands - defined by hydric soils, vegetation, and hydrology – perceived as "wasted space" and were converted to other uses – “By 1984, over half (54%) of all the wetlands in the United States were drained or filled for development or agriculture.“ Converted wetlands – wetlands that have been drained, dredged, filled or leveled or where woody vegetation has been removed Agricultural wetlands - cultivated lands that are modified former wetland areas, and which still exhibit evidence of soil saturation https://www.nrcs.usda.gov/wps/portal/nrcs/main/national/water/wetlands/
- 5. Background Increased awareness of the environmental benefits associated with wetlands prompted Congress to enact the Wetland Conservation Compliance Provisions of the Farm Bill in 1985. – Farmers who drain, clear trees, fill, or otherwise manipulate wetlands so that they can be cropped, may lose eligibility for USDA programs. – Before doing any alteration to a wet area, including clearing trees or maintenance of existing drainage, farmers should contact NRCS for a wetland determination. The Wetland Compliance provisions are the only laws that afford protection to many wetland types.
- 6. Where in the world is New Jersey?
- 7. ~7,700 square miles or ~5,000,000 acres 21 counties New York Philadelphia • The most densely populated state in the country • The Garden State • Ranks 8th for nursery and horticultural sales • Vegetable farming • Horses
- 8. Analysis Original question: What is the extent and location of wetlands conversions to agricultural uses since 1985? Available Datasets New Jersey’s Land Use/Land Cover datasets • 1986 Land Use/Land Cover • 1995/97 update • 2002 update • 2007 update • 2012 update • 2015 update Original question, revised, due to available datasets: “…between 1986 and 2012” Note: The wetlands described here were photo-interpreted. They are not on-the-ground delineations.
- 9. Analysis NJ’s Land Use/Land Cover Data – Modified Anderson Classification System 1000 Urban 2000 Agriculture 2140 Agricultural wetlands (modified) 3000 Range 4000 Forest 5000 Water 6000 Wetlands 7000 Barren
- 10. Land Use Change in NJ 1986 - 2012 New Jersey ~5,000,000 acres Units = acres 1986 2012 Change 1000Urban 1,252,138 1,573,836 321,698 2000Agriculture 818,592 618,246 (200,347) 4000Forest 1,614,891 1,527,740 (87,152) 5000Water 248,052 1,067,097 819,045 6000Wetlands 940,442 900,380 (40,062) 7000Barren 71,646 55,341 (16,305) 8000Managed Wetlands 7,988 n/a Grand Total 4,955,736 5,744,652 796,879
- 11. Land Use Change in NJ 1986 – 2012
- 12. What is the extent and location of wetland conversions to agricultural uses between 1986 and 2012?
- 13. Step 1 Select all “ModAg” polygons from the 2012 dataset 69,450 acres
- 14. Step 2 Intersect the 2012 Ag Wetlands with the 1986 Land Use/Land Cover layer to create a new layer that shows the prior land use for the 2012 Ag Wetland polygons.
- 15. Step 3 Select the 1986 wetlands from the output of Step 2 New layer that shows wetlands that were converted to ag uses between 1986 and 2012.
- 16. Results 9,492 acres of wetlands were converted to ag uses 8,842 polygons • sizes ranged from very tiny (slivers) to 53 acres • average polygon size: ~1 acre
- 17. Summary of Results 1) Types of wetlands that were converted 2) Summary of conversions by field office 3) Visual examples for staff training purposes
- 18. 1) Types of Wetlands that were Converted LAND_USE LABEL GISACRES FREQUENCY average acreage 6240HERBACEOUS WETLANDS 3,450.93 1,831 1.8 6210DECIDUOUS WOODED WETLANDS 2,234.12 3,851 0.5 6231DECIDUOUS SCRUB/SHRUB WETLANDS 1,472.83 1,474 0.9 6232CONIFEROUS SCRUB/SHRUB WETLANDS 383.13 71 5.3 6220CONIFEROUS WOODED WETLANDS 186.07 225 0.8 6252MIXED FORESTED WETLANDS (CONIFEROUS DOM.) 181.61 249 0.7 6251MIXED FORESTED WETLANDS (DECIDUOUS DOM.) 161.10 330 0.4 6233MIXED SCRUB/SHRUB WETLANDS (DECIDUOUS DOM.) 160.79 147 1.0 6234MIXED SCRUB/SHRUB WETLANDS (CONIFEROUS DOM.) 83.32 86 0.9 6221ATLANTIC WHITE CEDAR WETLANDS 77.43 51 1.5 6110SALINE MARSHES 23.79 30 0.7 6120FRESHWATER TIDAL MARSHES 8.04 24 0.3
- 19. 2) Summary by Field Office acres of wetlands converted to ag wetlands by 2012 total acres of wetlands in 1986 % of wetlands converted Hackettstown (7 counties) 1,660.51 119,904.48 1.4% Frenchtown (3 counties) 1,001.31 52,459.99 1.9% Freehold (3 counties) 1,825.65 122,809.79 1.5% Columbus (3 counties) 2,781.14 257,896.30 1.1% Woodstown (2 counties) 1,029.24 88,756.00 1.2% Vineland (3 counties) 1,194.75 253,893.74 0.5% Total 9,492.58 895,720.30 1.1%
- 20. 3) Visual Examples New Jersey Aerial Imagery Datasets / Orthophotography • 2012 imagery • corresponds to the 2012 Land Use/Land Cover layer • 1986 imagery • not available • 1995 imagery • earliest, readily available and usable aerial photography available statewide
- 22. Limitations • Without 1986 imagery, we cannot verify the original land cover classification. • This study can only be used to verify conversions that happened since 1995. • The following slides show examples of verified conversions since 1995.
- 23. Example 1. Camden County Deciduous Wooded Wetland 1.8 acres 2012 1995
- 24. Example 2. Burlington County Deciduous Scrub/Shrub Wetland 20 acres 2012 1995
- 25. Example 3. Cumberland County Deciduous Scrub/Shrub Wetland 1 acre 2012 1995
- 26. Example 4. Ocean County Coniferous Wooded Wetland .8 acres 2012 1995
- 27. Example 5. Burlington County Mixed Forested (Coniferous Dom.) Wetland 6 acres 2012 1995
- 28. Final Question Of the 9,492 acres of wetlands that were converted to ag between 1986 and 2012, how many acres were on lands that NRCS has worked on? Use GIS to overlay final results with Common Land Unit layer. Result: 81% (7,668 acres)
- 29. Conclusions ~9,000 acres of wetland conversions to ag uses may have occurred in NJ since 1986. This may be an overestimate. Next Steps Present this information to field office staff to raise awareness of the issue. Consider using imagery from 1980s to verify original land use classification and accuracy of results presented here. USDA-NHAP scans from the 1980s Not georeferenced, not statewide, not readily available But we are in the process of having the 1980s imagery processed so that we can use it in the future.
- 30. Questions? Trish Long GIS Specialist trish.long@usda.gov USDA-Natural Resources Conservation Service 220 Davidson Ave Somerset, NJ 08873 732-537-6064 www.nj.nrcs.usda.gov
Hinweis der Redaktion
- I am a GIS Specialist with NRCS-NJ. a project I worked on over the last several months. I am not a wetlands expert. But I definitely learned a lot about wetlands while working on this project.
- My supervisor asked me to look into wetland conversions based on some things she was seeing in our field offices. We wanted to quantify the extent and location of wetland conversions in NJ. There was concern that the findings from this study --- locations of potentially illegal wetland conversions --- would be controversial. But the focus of this project was to understand where (and when) conversions were occurring with the goal of educating our field staff to help prevent illegal conversions in the future. (It us up to folks above me, to decide what to do with the information presented here.)
- Here is my outline. ~30 slides total
- Some definitions Wetlands – soils, veg, hydro Converted – has been drained Ag wetland – former wetland area that is now used for agriculture This slide also includes some facts about wetlands losses in the US going back to 1984.
- The mid-1980s were important years in terms of wetland protections. WC Provisions were passed in 1985. The last statement on this slide emphasizes the importance of the WC provisions.
- For those who don’t know where it is, I have this slide. NJ is the 4th smallest state in the US . (RI, DE, CT are smaller)
- NJ is the most densely populated state in the country. But we are very proud to be the Garden State. As far as agriculture, NJ ranks 8th in the nation for nursery and horticultural sales. Vegetable farming and the horse industry are also big in NJ.
- In NJ, we actually have several statewide Land Use/Land Cover datasets.
- NJ uses a Modified Anderson LC Classification System. These are the Level 1 Categories. For this project, we were interested in all land that was in the “2140 Ag Wetlands” category (also referred to as “ModAg,”) in 2012. In looking at the land cover datasets, I found myself asking some more general questions about NJ’s land cover datasets…
- First, I looked at all Level 1 land cover categories. Looking at the numbers in the table: Urban-increase expected Ag-decrease expected Forest-decrease expected Water-big increase-unexpected!? --- explained by the next slide Wetlands-decrease-expected Barren-decrease Grand total-increase unexpected!
- This slide explains why there was a huge increase in water (and total acreage) in the state. …shows the importance of understanding the data and any changes that may have occurred in the mapping methodology over the years.
- Getting back to the question we were after…
- The next few slides show other ways of looking at the results.
- 12 types in all.
- Overall, the percentages are very low. What do these conversions look like?
- (Here is where I learned the most about our datasets and the conversions that had actually occurred.)
- Here is an example showing the 1986 land cover data It is labeled as a few different land cover types. But look at the skinny red polygons---labeled as cranberry bog, a type of ag wetland. But the interior is labeled as coniferous scrub/shrub wetlands. The fact that these red polygons were classified as cranberry bog in ‘86 makes me think the interior area was a cranberry bog in 1986 as well. This makes me wonder about quality control on the 1986 dataset. (This was the first time NJ had created a statewide lc dataset.) In the 1995 imagery, all this land is clearly Mod Ag. We know this area was converted to Mod Ag at some point. But without the 1986 imagery, there is no way to know if the conversion occurred before 1986 or not. There were lots of examples like this. I’m not going to show you any more of those, because the goal was to find areas where we can definitely confirm that a wetland was converted since 1986.
- 22
- After telling our Assistant State Conservationist for Programs about these results, she asked this question. Because some conversions may have occurred before 1986, the 9,000 acre number here may be an overestimate. But it does seem to indicate lack of attention to wetland conversions.
- It will be up to folks above me to decide how to respond to the conversions identified here.