diff --git a/climada/util/constants.py b/climada/util/constants.py
index 90f352218..c338c4e4c 100644
--- a/climada/util/constants.py
+++ b/climada/util/constants.py
@@ -45,11 +45,6 @@
 
 import matplotlib as mpl
 
-# pylint: disable=unused-import
-# without importing numpy ahead of fiona the debugger may run into an error
-import numpy
-from fiona.crs import from_epsg
-
 from .config import CONFIG
 
 SYSTEM_DIR = CONFIG.local_data.system.dir(create=False)
@@ -212,9 +207,6 @@
 DEF_CRS = f"EPSG:{DEF_EPSG}"
 """Default coordinate reference system WGS 84, str, for pyproj and rasterio CRS.from_string()"""
 
-DEF_CRS_FIONA = from_epsg(DEF_EPSG)
-"""Default coordinate reference system WGS 84, dict, for fiona interface"""
-
 cm_data1 = [
     [0.00000000, 0.00000000, 0.00000000],
     [0.00032031, 0.00020876, 0.00015576],
diff --git a/requirements/env_climada.yml b/requirements/env_climada.yml
index c4588ca6d..6e42d55b3 100644
--- a/requirements/env_climada.yml
+++ b/requirements/env_climada.yml
@@ -3,7 +3,7 @@ channels:
   - conda-forge
   - nodefaults
 dependencies:
-  - affine>=2.4,<3.0
+  - affine>=2.4,<3.0  # see #1311, affine 3.0 cannot read metadata from hdf5 files written by climada < 6.1
   - bayesian-optimization>=1.5,<2.0
   - bottleneck>=1.6
   - cartopy>=0.25